LAN8720A/LAN8720Ai Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support PRODUCT FEATURES Datasheet Highlights Key Benefits (cid:132) Single-Chip Ethernet Physical Layer Transceiver (cid:132) High-Performance 10/100 Ethernet Transceiver (PHY) — Compliant with IEEE802.3/802.3u (Fast Ethernet) (cid:132) Comprehensive flexPWR® Technology — Compliant with ISO 802-3/IEEE 802.3 (10BASE-T) — Loop-back modes — Flexible Power Management Architecture — Auto-negotiation — LVCMOS Variable I/O voltage range: +1.6V to +3.6V — Automatic polarity detection and correction — Integrated 1.2V regulator — Link status change wake-up detection (cid:132) HP Auto-MDIX support — Vendor specific register functions (cid:132) Miniature 24-pin QFN lead-free RoHS compliant — Supports the reduced pin count RMII interface package (4 x 4 x 0.85mm height). (cid:132) Power and I/Os — Various low power modes — Integrated power-on reset circuit Target Applications — Two status LED outputs — Latch-Up Performance Exceeds 150mA per EIA/JESD (cid:132) Set-Top Boxes 78, Class II (cid:132) Networked Printers and Servers — May be used with a single 3.3V supply (cid:132) Test Instrumentation (cid:132) Additional Features — Ability to use a low cost 25Mhz crystal for reduced BOM (cid:132) LAN on Motherboard (cid:132) Embedded Telecom Applications (cid:132) Packaging — 24-pin QFN (4x4 mm) Lead-Free RoHS Compliant (cid:132) Video Record/Playback Systems package with RMII (cid:132) Cable Modems/Routers (cid:132) Environmental (cid:132) DSL Modems/Routers — Extended commercial temperature range (cid:132) Digital Video Recorders (0°C to +85°C) — Industrial temperature range version available (cid:132) IP and Video Phones (-40°C to +85°C) (cid:132) Wireless Access Points (cid:132) Digital Televisions (cid:132) Digital Media Adaptors/Servers (cid:132) Gaming Consoles (cid:132) POE Applications (Refer to SMSC Application Note 17.18) SMSC LAN8720A/LAN8720Ai Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Order Numbers: LAN8720A-CP-TR for 24-pin QFN lead-free RoHS compliant package (0 to +85°C temp) LAN8720Ai-CP-TR for 24-pin QFN lead-free RoHS compliant package (-40 to +85°C temp) Reel size is 4,000. This product meets the halogen maximum concentration values per IEC61249-2-21 For RoHS compliance and environmental information, please visit www.smsc.com/rohs Please contact your SMSC sales representative for additional documentation related to this product such as application notes, anomaly sheets, and design guidelines. Copyright © 2012 SMSC or its subsidiaries. All rights reserved. Circuit diagrams and other information relating to SMSC products are included as a means of illustrating typical applications. Consequently, complete information sufficient for construction purposes is not necessarily given. Although the information has been checked and is believed to be accurate, no responsibility is assumed for inaccuracies. SMSC reserves the right to make changes to specifications and product descriptions at any time without notice. Contact your local SMSC sales office to obtain the latest specifications before placing your product order. The provision of this information does not convey to the purchaser of the described semiconductor devices any licenses under any patent rights or other intellectual property rights of SMSC or others. All sales are expressly conditional on your agreement to the terms and conditions of the most recently dated version of SMSC's standard Terms of Sale Agreement dated before the date of your order (the "Terms of Sale Agreement"). The product may contain design defects or errors known as anomalies which may cause the product's functions to deviate from published specifications. Anomaly sheets are available upon request. SMSC products are not designed, intended, authorized or warranted for use in any life support or other application where product failure could cause or contribute to personal injury or severe property damage. Any and all such uses without prior written approval of an Officer of SMSC and further testing and/or modification will be fully at the risk of the customer. Copies of this document or other SMSC literature, as well as the Terms of Sale Agreement, may be obtained by visiting SMSC’s website at http://www.smsc.com. SMSC is a registered trademark of Standard Microsystems Corporation (“SMSC”). Product names and company names are the trademarks of their respective holders. The Microchip name and logo, and the Microchip logo are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. SMSC DISCLAIMS AND EXCLUDES ANY AND ALL WARRANTIES, INCLUDING WITHOUT LIMITATION ANY AND ALL IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, TITLE, AND AGAINST INFRINGEMENT AND THE LIKE, AND ANY AND ALL WARRANTIES ARISING FROM ANY COURSE OF DEALING OR USAGE OF TRADE. IN NO EVENT SHALL SMSC BE LIABLE FOR ANY DIRECT, INCIDENTAL, INDIRECT, SPECIAL, PUNITIVE, OR CONSEQUENTIAL DAMAGES; OR FOR LOST DATA, PROFITS, SAVINGS OR REVENUES OF ANY KIND; REGARDLESS OF THE FORM OF ACTION, WHETHER BASED ON CONTRACT; TORT; NEGLIGENCE OF SMSC OR OTHERS; STRICT LIABILITY; BREACH OF WARRANTY; OR OTHERWISE; WHETHER OR NOT ANY REMEDY OF BUYER IS HELD TO HAVE FAILED OF ITS ESSENTIAL PURPOSE, AND WHETHER OR NOT SMSC HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. Revision 1.4 (08-23-12) 2 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Table of Contents Chapter1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.1 General Terms and Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.2 General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Chapter2 Pin Description and Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1 Pin Assignments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.2 Buffer Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Chapter3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.1 Transceiver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.1.1 100BASE-TX Transmit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.1.2 100BASE-TX Receive. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.1.3 10BASE-T Transmit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3.1.4 10BASE-T Receive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.2 Auto-negotiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.2.1 Parallel Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.2.2 Restarting Auto-negotiation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.2.3 Disabling Auto-negotiation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.2.4 Half vs. Full Duplex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.3 HP Auto-MDIX Support. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.4 MAC Interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.4.1 RMII. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.5 Serial Management Interface (SMI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3.6 Interrupt Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.6.1 Primary Interrupt System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.6.2 Alternate Interrupt System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 3.7 Configuration Straps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 3.7.1 PHYAD[0]: PHY Address Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 3.7.2 MODE[2:0]: Mode Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 3.7.3 REGOFF: Internal +1.2V Regulator Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 3.7.4 nINTSEL: nINT/REFCLKO Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3.8 Miscellaneous Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 3.8.1 LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 3.8.2 Variable Voltage I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 3.8.3 Power-Down Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 3.8.4 Isolate Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 3.8.5 Resets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 3.8.6 Carrier Sense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 3.8.7 Link Integrity Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 3.8.8 Loopback Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 3.9 Application Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 3.9.1 Simplified System Level Application Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 3.9.2 Power Supply Diagram (1.2V Supplied by Internal Regulator) . . . . . . . . . . . . . . . . . . . . 43 3.9.3 Power Supply Diagram (1.2V Supplied by External Source). . . . . . . . . . . . . . . . . . . . . . 44 3.9.4 Twisted-Pair Interface Diagram (Single Power Supply). . . . . . . . . . . . . . . . . . . . . . . . . . 45 3.9.5 Twisted-Pair Interface Diagram (Dual Power Supplies) . . . . . . . . . . . . . . . . . . . . . . . . . 46 Chapter4 Register Descriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 4.1 Register Nomenclature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 4.2 Control and Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 4.2.1 Basic Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 SMSC LAN8720A/LAN8720Ai 3 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 4.2.2 Basic Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.2.3 PHY Identifier 1 Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 4.2.4 PHY Identifier 2 Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4.2.5 Auto Negotiation Advertisement Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 4.2.6 Auto Negotiation Link Partner Ability Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 4.2.7 Auto Negotiation Expansion Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 4.2.8 Mode Control/Status Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 4.2.9 Special Modes Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 4.2.10 Symbol Error Counter Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 4.2.11 Special Control/Status Indications Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.2.12 Interrupt Source Flag Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 4.2.13 Interrupt Mask Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4.2.14 PHY Special Control/Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 Chapter5 Operational Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 5.1 Absolute Maximum Ratings*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 5.2 Operating Conditions**. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 5.3 Power Consumption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 5.3.1 REF_CLK In Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 5.3.2 REF_CLK Out Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 5.4 DC Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 5.5 AC Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 5.5.1 Equivalent Test Load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 5.5.2 Power Sequence Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 5.5.3 Power-On nRST & Configuration Strap Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 5.5.4 RMII Interface Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 5.5.5 SMI Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 5.6 Clock Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Chapter6 Package Outline. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Chapter7 Datasheet Revision History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 Revision 1.4 (08-23-12) 4 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet List of Figures Figure1.1 System Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Figure1.2 Architectural Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Figure2.1 24-QFN Pin Assignments (TOP VIEW) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Figure3.1 100BASE-TX Transmit Data Path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Figure3.2 100BASE-TX Receive Data Path. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Figure3.3 Relationship Between Received Data and Specific MII Signals . . . . . . . . . . . . . . . . . . . . . . 21 Figure3.4 Direct Cable Connection vs. Cross-over Cable Connection . . . . . . . . . . . . . . . . . . . . . . . . . 26 Figure3.5 MDIO Timing and Frame Structure - READ Cycle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Figure3.6 MDIO Timing and Frame Structure - WRITE Cycle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Figure3.7 External 50MHz clock sources the REF_CLK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Figure3.8 Sourcing REF_CLK from a 25MHz Crystal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Figure3.9 Sourcing REF_CLK from External 25MHz Source. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Figure3.10 LED1/REGOFF Polarity Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Figure3.11 LED2/nINTSEL Polarity Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Figure3.12 Near-end Loopback Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Figure3.13 Far Loopback Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Figure3.14 Connector Loopback Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Figure3.15 Simplified System Level Application Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Figure3.16 Power Supply Diagram (1.2V Supplied by Internal Regulator) . . . . . . . . . . . . . . . . . . . . . . . 43 Figure3.17 Power Supply Diagram (1.2V Supplied by External Source). . . . . . . . . . . . . . . . . . . . . . . . . 44 Figure3.18 Twisted-Pair Interface Diagram (Single Power Supply). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Figure3.19 Twisted-Pair Interface Diagram (Dual Power Supplies). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Figure5.1 Output Equivalent Test Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 Figure5.2 Power Sequence Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Figure5.3 Power-On nRST & Configuration Strap Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Figure5.4 RMII Timing (REF_CLK Out Mode). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 Figure5.5 RMII Timing (REF_CLK In Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Figure5.6 SMI Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 SMSC LAN8720A/LAN8720Ai 5 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet List of Tables Table2.1 RMII Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Table2.2 LED Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Table2.3 Serial Management Interface (SMI) Pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Table2.4 Ethernet Pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Table2.5 Miscellaneous Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Table2.6 Analog Reference Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Table2.7 Power Pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Table2.8 24-QFN Package Pin Assignments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Table2.9 Buffer Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Table3.1 4B/5B Code Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Table3.2 Interrupt Management Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Table3.3 Alternative Interrupt System Management Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Table3.4 MODE[2:0] Bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Table3.5 Pin Names for Mode Bits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Table3.6 nINTSEL Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Table4.1 Register Bit Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Table4.2 SMI Register Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Table5.1 Device Only Current Consumption and Power Dissipation (REF_CLK In Mode) . . . . . . . . . . 64 Table5.2 Device Only Current Consumption and Power Dissipation (REF_CLK Out Mode). . . . . . . . . 65 Table5.3 Non-Variable I/O Buffer Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Table5.4 Variable I/O Buffer Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 Table5.5 100BASE-TX Transceiver Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 Table5.6 10BASE-T Transceiver Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 Table5.7 Power Sequence Timing Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Table5.8 Power-On nRST & Configuration Strap Timing Values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Table5.9 RMII Timing Values (REF_CLK Out Mode). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 Table5.10RMII Timing Values (REF_CLK In Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Table5.11RMII CLKIN (REF_CLK) Timing Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Table5.12SMI Timing Values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Table5.13Crystal Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Table7.1 Customer Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 Revision 1.4 (08-23-12) 6 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Chapter 1 Introduction 1.1 General Terms and Conventions The following is list of the general terms used throughout this document: BYTE 8-bits FIFO First In First Out buffer; often used for elasticity buffer MAC Media Access Controller RMIITM Reduced Media Independent InterfaceTM N/A Not Applicable X Indicates that a logic state is “don’t care” or undefined. RESERVED Refers to a reserved bit field or address. Unless otherwise noted, reserved bits must always be zero for write operations. Unless otherwise noted, values are not guaranteed when reading reserved bits. Unless otherwise noted, do not read or write to reserved addresses. SMI Serial Management Interface 1.2 General Description The LAN8720A/LAN8720Ai is a low-power 10BASE-T/100BASE-TX physical layer (PHY) transceiver with variable I/O voltage that is compliant with the IEEE 802.3-2005 standards. The LAN8720A/LAN8720Ai supports communication with an Ethernet MAC via a standard RMII interface. It contains a full-duplex 10-BASE-T/100BASE-TX transceiver and supports 10Mbps (10BASE-T) and 100Mbps (100BASE-TX) operation. The LAN8720A/LAN8720Ai implements auto- negotiation to automatically determine the best possible speed and duplex mode of operation. HP Auto-MDIX support allows the use of direct connect or cross-over LAN cables. The LAN8720A/LAN8720Ai supports both IEEE 802.3-2005 compliant and vendor-specific register functions. However, no register access is required for operation. The initial configuration may be selected via the configuration pins as described in Section 3.7, "Configuration Straps," on page31. Register-selectable configuration options may be used to further define the functionality of the transceiver. Per IEEE 802.3-2005 standards, all digital interface pins are tolerant to 3.6V. The device can be configured to operate on a single 3.3V supply utilizing an integrated 3.3V to 1.2V linear regulator. The linear regulator may be optionally disabled, allowing usage of a high efficiency external regulator for lower system power dissipation. The LAN8720A/LAN8720Ai is available in both extended commercial and industrial temperature range versions. A typical system application is shown in Figure1.1. SMSC LAN8720A/LAN8720Ai 7 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 10/100 Ethernet RMII LAN8720A/ MDI Transformer RJ45 LAN8720Ai MAC Mode LED Crystal or Clock Oscillator Figure1.1 System Block Diagram MODE[0:2] Mode Control HP Auto-MDIX Auto- 100M TX 100M TXP/TXN nRST Reset Control Negotiation Logic Transmitter Transmitter RXP/RXN RMIISEL SMI Management 10M TX 10M MDIX TXD[0:1] Control Logic Transmitter Control TXEN XTAL1/CLKIN PLL XTAL2 RXD[0:1] RXER MII Logic 10L0oMg icRX DDSaPEtaqC RuSlaoeylccizskoetverermy : AnDailgoigta-tlo- GInetneerrruaptot r nINT R LED1 CRS_DV 100M PLL LEDs MDC Receiver LED2 10M RX Squeltch MDIO Logic & Filters Central Bias RBIAS 10M PLL PHY Address PHYAD0 Latches LAN8720A/LAN8720Ai Figure1.2 Architectural Overview Revision 1.4 (08-23-12) 8 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Chapter 2 Pin Description and Configuration O K L C F E R XD1 XD0 XEN RST NT/ DC T T T n nI M 8 7 6 5 4 3 1 1 1 1 1 1 VDD1A 19 12 MDIO SMSC LAN8720A/LAN8720Ai TXN 20 11 CRS_DV/MODE2 24 PIN QFN (TOP VIEW) TXP 21 10 RXER/PHYAD0 VSS RXN 22 9 VDDIO RXP 23 8 RXD0/MODE0 RBIAS 24 7 RXD1/MODE1 1 2 3 4 5 6 A L F 2 N R VDD2 2/nINTSE 1/REGOF XTAL AL1/CLKI VDDC D D T E E X L L NOTE: Exposed pad (VSS) on bottom of package must be connected to ground Figure2.1 24-QFN Pin Assignments (TOP VIEW) Note: When a lower case “n” is used at the beginning of the signal name, it indicates that the signal is active low. For example, nRST indicates that the reset signal is active low. Note: The buffer type for each signal is indicated in the BUFFER TYPE column. A description of the buffer types is provided in Section2.2. SMSC LAN8720A/LAN8720Ai 9 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Table2.1 RMII Signals BUFFER NUM PINS NAME SYMBOL TYPE DESCRIPTION Transmit TXD0 VIS The MAC transmits data to the transceiver using 1 Data 0 this signal. Transmit TXD1 VIS The MAC transmits data to the transceiver using 1 Data 1 this signal. Transmit TXEN VIS Indicates that valid transmission data is present 1 Enable (PD) on TXD[1:0]. Receive RXD0 VO8 Bit 0 of the 2 data bits that are sent by the Data 0 transceiver on the receive path. PHY MODE0 VIS Combined with MODE1 and MODE2, this Operating (PU) configuration strap sets the default PHY mode. 1 Mode 0 See Note2.1 for more information on Configuration configuration straps. Strap Note: Refer to Section 3.7.2, "MODE[2:0]: Mode Configuration," on page31 for additional details. Receive RXD1 VO8 Bit 1 of the 2 data bits that are sent by the Data 1 transceiver on the receive path. PHY MODE1 VIS Combined with MODE0 and MODE2, this Operating (PU) configuration strap sets the default PHY mode. 1 Mode 1 Configuration See Note2.1 for more information on configuration straps. Strap Note: Refer to Section 3.7.2, "MODE[2:0]: Mode Configuration," on page31 for additional details. Receive Error RXER VO8 This signal is asserted to indicate that an error was detected somewhere in the frame presently being transferred from the transceiver. PHY Address PHYAD0 VIS This configuration strap sets the transceiver’s 0 (PD) SMI address. 1 Configuration Strap See Note2.1 for more information on configuration straps. Note: Refer to Section 3.7.1, "PHYAD[0]: PHY Address Configuration," on page31 for additional information. Revision 1.4 (08-23-12) 10 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Table2.1 RMII Signals (continued) BUFFER NUM PINS NAME SYMBOL TYPE DESCRIPTION Carrier Sense CRS_DV VO8 This signal is asserted to indicate the receive / Receive medium is non-idle. When a 10BASE-T packet is Data Valid received, CRS_DV is asserted, but RXD[1:0] is held low until the SFD byte (10101011) is received. Note: Per the RMII standard, transmitted data is not looped back onto the receive data pins in 10BASE-T half-duplex mode. 1 PHY MODE2 VIS Combined with MODE0 and MODE1, this Operating (PU) configuration strap sets the default PHY mode. Mode 2 Configuration See Note2.1 for more information on configuration straps. Strap Note: Refer to Section 3.7.2, "MODE[2:0]: Mode Configuration," on page31 for additional details. Note2.1 Configuration strap values are latched on power-on reset and system reset. Configuration straps are identified by an underlined symbol name. Signals that function as configuration straps must be augmented with an external resistor when connected to a load. Refer to Section 3.7, "Configuration Straps," on page31 for additional information. Table2.2 LED Pins BUFFER NUM PINS NAME SYMBOL TYPE DESCRIPTION LED 1 LED1 O12 Link activity LED Indication. This pin is driven active when a valid link is detected and blinks when activity is detected. Note: Refer to Section 3.8.1, "LEDs," on page37 for additional LED information. Regulator Off REGOFF IS This configuration strap is used to disable the Configuration (PD) internal 1.2V regulator. When the regulator is Strap disabled, external 1.2V must be supplied to VDDCR. 1 (cid:132)When REGOFF is pulled high to VDD2A with an external resistor, the internal regulator is disabled. (cid:132)When REGOFF is floating or pulled low, the internal regulator is enabled (default). See Note2.2 for more information on configuration straps. Note: Refer to Section 3.7.3, "REGOFF: Internal +1.2V Regulator Configuration," on page32 for additional details. SMSC LAN8720A/LAN8720Ai 11 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Table2.2 LED Pins (continued) BUFFER NUM PINS NAME SYMBOL TYPE DESCRIPTION LED 2 LED2 O12 Link Speed LED Indication. This pin is driven active when the operating speed is 100Mbps. It is inactive when the operating speed is 10Mbps or during line isolation. Note: Refer to Section 3.8.1, "LEDs," on page37 for additional LED information. nINT/ nINTSEL IS This configuration strap selects the mode of the REFCLKO (PU) nINT/REFCLKO pin. Function Select (cid:132)When nINTSEL is floated or pulled to VDD2A, 1 Configuration nINT is selected for operation on the Strap nINT/REFCLKO pin (default). (cid:132)When nINTSEL is pulled low to VSS, REFCLKO is selected for operation on the nINT/REFCLKO pin. See Note2.2 for more information on configuration straps. Note: Refer to See Section 3.8.1.2, "nINTSEL and LED2 Polarity Selection," on page37 for additional information. Note2.2 Configuration strap values are latched on power-on reset and system reset. Configuration straps are identified by an underlined symbol name. Signals that function as configuration straps must be augmented with an external resistor when connected to a load. Refer to Section 3.7, "Configuration Straps," on page31 for additional information. Table2.3 Serial Management Interface (SMI) Pins BUFFER NUM PINS NAME SYMBOL TYPE DESCRIPTION SMI Data MDIO VIS/ Serial Management Interface data input/output 1 Input/Output VOD8 1 SMI Clock MDC VIS Serial Management Interface clock Table2.4 Ethernet Pins BUFFER NUM PINS NAME SYMBOL TYPE DESCRIPTION Ethernet TXP AIO Transmit/Receive Positive Channel 1 TX/RX 1 Positive Channel 1 Ethernet TXN AIO Transmit/Receive Negative Channel 1 TX/RX 1 Negative Channel 1 Revision 1.4 (08-23-12) 12 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Table2.4 Ethernet Pins (continued) BUFFER NUM PINS NAME SYMBOL TYPE DESCRIPTION Ethernet RXP AIO Transmit/Receive Positive Channel 2 TX/RX 1 Positive Channel 2 Ethernet RXN AIO Transmit/Receive Negative Channel 2 TX/RX 1 Negative Channel 2 Table2.5 Miscellaneous Pins BUFFER NUM PINS NAME SYMBOL TYPE DESCRIPTION External XTAL1 ICLK External crystal input Crystal Input 1 External CLKIN ICLK Single-ended clock oscillator input. Clock Input Note: When using a single ended clock oscillator, XTAL2 should be left unconnected. External XTAL2 OCLK External crystal output 1 Crystal Output External nRST VIS System reset. This signal is active low. 1 Reset (PU) Interrupt nINT VOD8 Active low interrupt output. Place an external Output (PU) resistor pull-up to VDDIO. Note: Refer to Section 3.6, "Interrupt Management," on page29 for additional details on device interrupts. Note: Refer to Section 3.8.1.2, "nINTSEL and LED2 Polarity Selection," on page37 for details on how the nINTSEL configuration strap is used to determine the function of this pin. 1 Reference REFCLKO VO8 This optional 50MHz clock output is derived from Clock Output the 25MHz crystal oscillator. REFCLKO is selectable via the nINTSEL configuration strap. Note: Refer Section 3.7.4.2, "REF_CLK Out Mode," on page34 for additional details. Note: Refer to Section 3.8.1.2, "nINTSEL and LED2 Polarity Selection," on page37 for details on how the nINTSEL configuration strap is used to determine the function of this pin. SMSC LAN8720A/LAN8720Ai 13 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Table2.6 Analog Reference Pins BUFFER NUM PINS NAME SYMBOL TYPE DESCRIPTION External 1% RBIAS AI This pin requires connection of a 12.1k ohm (1%) Bias Resistor resistor to ground. Input Refer to the LAN8720A/LAN8720Ai reference 1 schematic for connection information. Note: The nominal voltage is 1.2V and the resistor will dissipate approximately 1mW of power. Table2.7 Power Pins BUFFER NUM PINS NAME SYMBOL TYPE DESCRIPTION +1.6V to VDDIO P +1.6V to +3.6V variable I/O power +3.6V 1 Variable I/O Refer to the LAN8720A/LAN8720Ai reference Power schematic for connection information. +1.2V Digital VDDCR P Supplied by the on-chip regulator unless Core Power configured for regulator off mode via the Supply REGOFF configuration strap. Refer to the LAN8720A/LAN8720Ai reference 1 schematic for connection information. Note: 1 uF and 470 pF decoupling capacitors in parallel to ground should be used on this pin. +3.3V VDD1A P +3.3V Analog Port Power to Channel 1 Channel 1 1 Analog Port Refer to the LAN8720A/LAN8720Ai reference Power schematic for connection information. +3.3V VDD2A P +3.3V Analog Port Power to Channel 2 and the Channel 2 internal regulator. 1 Analog Port Power Refer to the LAN8720A/LAN8720Ai reference schematic for connection information. Ground VSS P Common ground. This exposed pad must be 1 connected to the ground plane with a via array. Revision 1.4 (08-23-12) 14 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 2.1 Pin Assignments Table2.8 24-QFN Package Pin Assignments PIN NUM PIN NAME PIN NUM PIN NAME 1 VDD2A 13 MDC 2 LED2/nINTSEL 14 nINT/REFCLKO 3 LED1/REGOFF 15 nRST 4 XTAL2 16 TXEN 5 XTAL1/CLKIN 17 TXD0 6 VDDCR 18 TXD1 7 RXD1/MODE1 19 VDD1A 8 RXD0/MODE0 20 TXN 9 VDDIO 21 TXP 10 RXER/PHYAD0 22 RXN 11 CRS_DV/MODE2 23 RXP 12 MDIO 24 RBIAS SMSC LAN8720A/LAN8720Ai 15 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 2.2 Buffer Types Table2.9 Buffer Types BUFFER TYPE DESCRIPTION IS Schmitt-triggered input O12 Output with 12mA sink and 12mA source VIS Variable voltage Schmitt-triggered input VO8 Variable voltage output with 8mA sink and 8mA source VOD8 Variable voltage open-drain output with 8mA sink PU 50uA (typical) internal pull-up. Unless otherwise noted in the pin description, internal pull- ups are always enabled. Note: Internal pull-up resistors prevent unconnected inputs from floating. Do not rely on internal resistors to drive signals external to the device. When connected to a load that must be pulled high, an external resistor must be added. PD 50uA (typical) internal pull-down. Unless otherwise noted in the pin description, internal pull-downs are always enabled. Note: Internal pull-down resistors prevent unconnected inputs from floating. Do not rely on internal resistors to drive signals external to the device. When connected to a load that must be pulled low, an external resistor must be added. AI Analog input AIO Analog bi-directional ICLK Crystal oscillator input pin OCLK Crystal oscillator output pin P Power pin Note: The digital signals are not 5V tolerant. Refer to Section 5.1, "Absolute Maximum Ratings*," on page63 for additional buffer information. Note2.3 Sink and source capabilities are dependant on the VDDIO voltage. Refer to Section 5.1, "Absolute Maximum Ratings*," on page63 for additional information. Revision 1.4 (08-23-12) 16 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Chapter 3 Functional Description This chapter provides functional descriptions of the various device features. These features have been categorized into the following sections: (cid:132) Transceiver (cid:132) Auto-negotiation (cid:132) HP Auto-MDIX Support (cid:132) MAC Interface (cid:132) Serial Management Interface (SMI) (cid:132) Interrupt Management (cid:132) Configuration Straps (cid:132) Miscellaneous Functions (cid:132) Application Diagrams 3.1 Transceiver 3.1.1 100BASE-TX Transmit The 100BASE-TX transmit data path is shown in Figure3.1. Each major block is explained in the following subsections. PLL MAC Ext Ref_CLK 25MHz 4B/5B 25MHz by Scrambler RMII 50Mhz by 2 bits RMII by 4 bits Encoder 5 bits and PISO NRZI MLT-3 Tx 125 Mbps Serial NRZI MLT-3 Converter Converter Driver MLT-3 Magnetics MLT-3 RJ45 MLT-3 CAT-5 Figure3.1 100BASE-TX Transmit Data Path 3.1.1.1 100BASE-TX Transmit Data Across the RMII Interface The MAC controller drives the transmit data onto the TXD bus and asserts TXEN to indicate valid data. The data is latched by the transceiver’s RMII block on the rising edge of REF_CLK. The data is in the form of 2-bit wide 50MHz data. SMSC LAN8720A/LAN8720Ai 17 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.1.1.2 4B/5B Encoding The transmit data passes from the RMII block to the 4B/5B encoder. This block encodes the data from 4-bit nibbles to 5-bit symbols (known as “code-groups”) according to Table3.1. Each 4-bit data-nibble is mapped to 16 of the 32 possible code-groups. The remaining 16 code-groups are either used for control information or are not valid. The first 16 code-groups are referred to by the hexadecimal values of their corresponding data nibbles, 0 through F. The remaining code-groups are given letter designations with slashes on either side. For example, an IDLE code-group is /I/, a transmit error code-group is /H/, etc. Table3.1 4B/5B Code Table CODE RECEIVER TRANSMITTER GROUP SYM INTERPRETATION INTERPRETATION 11110 0 0 0000 DATA 0 0000 DATA 01001 1 1 0001 1 0001 10100 2 2 0010 2 0010 10101 3 3 0011 3 0011 01010 4 4 0100 4 0100 01011 5 5 0101 5 0101 01110 6 6 0110 6 0110 01111 7 7 0111 7 0111 10010 8 8 1000 8 1000 10011 9 9 1001 9 1001 10110 A A 1010 A 1010 10111 B B 1011 B 1011 11010 C C 1100 C 1100 11011 D D 1101 D 1101 11100 E E 1110 E 1110 11101 F F 1111 F 1111 11111 I IDLE Sent after /T/R until TXEN 11000 J First nibble of SSD, translated to “0101” Sent for rising TXEN following IDLE, else RXER 10001 K Second nibble of SSD, translated to Sent for rising TXEN “0101” following J, else RXER 01101 T First nibble of ESD, causes de-assertion Sent for falling TXEN of CRS if followed by /R/, else assertion of RXER 00111 R Second nibble of ESD, causes Sent for falling TXEN deassertion of CRS if following /T/, else assertion of RXER 00100 H Transmit Error Symbol Sent for rising TXER 00110 V INVALID, RXER if during RXDV INVALID Revision 1.4 (08-23-12) 18 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Table3.1 4B/5B Code Table (continued) CODE RECEIVER TRANSMITTER GROUP SYM INTERPRETATION INTERPRETATION 11001 V INVALID, RXER if during RXDV INVALID 00000 V INVALID, RXER if during RXDV INVALID 00001 V INVALID, RXER if during RXDV INVALID 00010 V INVALID, RXER if during RXDV INVALID 00011 V INVALID, RXER if during RXDV INVALID 00101 V INVALID, RXER if during RXDV INVALID 01000 V INVALID, RXER if during RXDV INVALID 01100 V INVALID, RXER if during RXDV INVALID 10000 V INVALID, RXER if during RXDV INVALID 3.1.1.3 Scrambling Repeated data patterns (especially the IDLE code-group) can have power spectral densities with large narrow-band peaks. Scrambling the data helps eliminate these peaks and spread the signal power more uniformly over the entire channel bandwidth. This uniform spectral density is required by FCC regulations to prevent excessive EMI from being radiated by the physical wiring. The seed for the scrambler is generated from the transceiver address, PHYAD, ensuring that in multiple-transceiver applications, such as repeaters or switches, each transceiver will have its own scrambler sequence. The scrambler also performs the Parallel In Serial Out conversion (PISO) of the data. 3.1.1.4 NRZI and MLT-3 Encoding The scrambler block passes the 5-bit wide parallel data to the NRZI converter where it becomes a serial 125MHz NRZI data stream. The NRZI is encoded to MLT-3. MLT-3 is a tri-level code where a change in the logic level represents a code bit “1” and the logic output remaining at the same level represents a code bit “0”. 3.1.1.5 100M Transmit Driver The MLT3 data is then passed to the analog transmitter, which drives the differential MLT-3 signal, on outputs TXP and TXN, to the twisted pair media across a 1:1 ratio isolation transformer. The 10BASE- T and 100BASE-TX signals pass through the same transformer so that common “magnetics” can be used for both. The transmitter drives into the 100Ω impedance of the CAT-5 cable. Cable termination and impedance matching require external components. 3.1.1.6 100M Phase Lock Loop (PLL) The 100M PLL locks onto reference clock and generates the 125MHz clock used to drive the 125 MHz logic and the 100BASE-TX transmitter. SMSC LAN8720A/LAN8720Ai 19 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.1.2 100BASE-TX Receive The 100BASE-TX receive data path is shown in Figure3.2. Each major block is explained in the following subsections. PLL MAC Ext Ref_CLK 25MHz 25MHz by by 4 bits 4B/5B 5 bits Descrambler RMII 50Mhz by 2 bits RMII Decoder and SIPO 125 Mbps Serial DSP: Timing NRZI NRZI MLT-3 MLT-3 recovery, Equalizer Converter Converter and BLW Correction A/D MLT-3 MLT-3 MLT-3 Magnetics RJ45 CAT-5 Converter 6 bit Data Figure3.2 100BASE-TX Receive Data Path 3.1.2.1 100M Receive Input The MLT-3 from the cable is fed into the transceiver (on inputs RXP and RXN) via a 1:1 ratio transformer. The ADC samples the incoming differential signal at a rate of 125M samples per second. Using a 64-level quanitizer, it generates 6 digital bits to represent each sample. The DSP adjusts the gain of the ADC according to the observed signal levels such that the full dynamic range of the ADC can be used. 3.1.2.2 Equalizer, Baseline Wander Correction and Clock and Data Recovery The 6 bits from the ADC are fed into the DSP block. The equalizer in the DSP section compensates for phase and amplitude distortion caused by the physical channel consisting of magnetics, connectors, and CAT- 5 cable. The equalizer can restore the signal for any good-quality CAT-5 cable between 1m and 150m. If the DC content of the signal is such that the low-frequency components fall below the low frequency pole of the isolation transformer, then the droop characteristics of the transformer will become significant and Baseline Wander (BLW) on the received signal will result. To prevent corruption of the received data, the transceiver corrects for BLW and can receive the ANSI X3.263-1995 FDDI TP-PMD defined “killer packet” with no bit errors. The 100M PLL generates multiple phases of the 125MHz clock. A multiplexer, controlled by the timing unit of the DSP, selects the optimum phase for sampling the data. This is used as the received recovered clock. This clock is used to extract the serial data from the received signal. Revision 1.4 (08-23-12) 20 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.1.2.3 NRZI and MLT-3 Decoding The DSP generates the MLT-3 recovered levels that are fed to the MLT-3 converter. The MLT-3 is then converted to an NRZI data stream. 3.1.2.4 Descrambling The descrambler performs an inverse function to the scrambler in the transmitter and also performs the Serial In Parallel Out (SIPO) conversion of the data. During reception of IDLE (/I/) symbols. the descrambler synchronizes its descrambler key to the incoming stream. Once synchronization is achieved, the descrambler locks on this key and is able to descramble incoming data. Special logic in the descrambler ensures synchronization with the remote transceiver by searching for IDLE symbols within a window of 4000 bytes (40us). This window ensures that a maximum packet size of 1514 bytes, allowed by the IEEE 802.3 standard, can be received with no interference. If no IDLE- symbols are detected within this time-period, receive operation is aborted and the descrambler re-starts the synchronization process. 3.1.2.5 Alignment The de-scrambled signal is then aligned into 5-bit code-groups by recognizing the /J/K/ Start-of-Stream Delimiter (SSD) pair at the start of a packet. Once the code-word alignment is determined, it is stored and utilized until the next start of frame. 3.1.2.6 5B/4B Decoding The 5-bit code-groups are translated into 4-bit data nibbles according to the 4B/5B table. The translated data is presented on the RXD[1:0] signal lines. The SSD, /J/K/, is translated to “0101 0101” as the first 2 nibbles of the MAC preamble. Reception of the SSD causes the transceiver to assert the receive data valid signal, indicating that valid data is available on the RXD bus. Successive valid code- groups are translated to data nibbles. Reception of either the End of Stream Delimiter (ESD) consisting of the /T/R/ symbols, or at least two /I/ symbols causes the transceiver to de-assert the carrier sense and receive data valid signals. Note: These symbols are not translated into data. 3.1.2.7 Receive Data Valid Signal The Receive Data Valid signal (RXDV) indicates that recovered and decoded nibbles are being presented on the RXD[1:0] outputs synchronous to RXCLK. RXDV becomes active after the /J/K/ delimiter has been recognized and RXD is aligned to nibble boundaries. It remains active until either the /T/R/ delimiter is recognized or link test indicates failure or SIGDET becomes false. RXDV is asserted when the first nibble of translated /J/K/ is ready for transfer over the Media Independent Interface (MII mode). CLEAR-TEXT J K 5 5 5 D data data data data T R Idle RX_CLK RX_DV RXD 5 5 5 5 5 D data data data data Figure3.3 Relationship Between Received Data and Specific MII Signals SMSC LAN8720A/LAN8720Ai 21 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.1.2.8 Receiver Errors During a frame, unexpected code-groups are considered receive errors. Expected code groups are the DATA set (0 through F), and the /T/R/ (ESD) symbol pair. When a receive error occurs, the RXER signal is asserted and arbitrary data is driven onto the RXD[1:0] lines. Should an error be detected during the time that the /J/K/ delimiter is being decoded (bad SSD error), RXER is asserted true and the value ‘1110’ is driven onto the RXD[1:0] lines. Note that the Valid Data signal is not yet asserted when the bad SSD error occurs. 3.1.2.9 100M Receive Data Across the RMII Interface The 2-bit data nibbles are sent to the RMII block. These data nibbles are clocked to the controller at a rate of 50MHz. The controller samples the data on the rising edge of XTAL1/CLKIN (REF_CLK). To ensure that the setup and hold requirements are met, the nibbles are clocked out of the transceiver on the falling edge of XTAL1/CLKIN (REF_CLK). 3.1.3 10BASE-T Transmit Data to be transmitted comes from the MAC layer controller. The 10BASE-T transmitter receives 4-bit nibbles from the MII at a rate of 2.5MHz and converts them to a 10Mbps serial data stream. The data stream is then Manchester-encoded and sent to the analog transmitter, which drives a signal onto the twisted pair via the external magnetics. The 10M transmitter uses the following blocks: (cid:132) MII (digital) (cid:132) TX 10M (digital) (cid:132) 10M Transmitter (analog) (cid:132) 10M PLL (analog) 3.1.3.1 10M Transmit Data Across the RMII Interface The MAC controller drives the transmit data onto the TXD bus. TXD[1:0] shall transition synchronously with respect to REF_CLK. When TXEN is asserted, TXD[1:0] are accepted for transmission by the device. TXD[1:0] shall be “00” to indicate idle when TXEN is deasserted. Values of TXD[1:0] other than “00” when TXEN is deasserted are reserved for out-of-band signalling (to be defined). Values other than “00” on TXD[1:0] while TXEN is deasserted shall be ignored by the device.TXD[1:0] shall provide valid data for each REF_CLK period while TXEN is asserted. In order to comply with legacy 10BASE-T MAC/Controllers, in half-duplex mode the transceiver loops back the transmitted data, on the receive path. This does not confuse the MAC/Controller since the COL signal is not asserted during this time. The transceiver also supports the SQE (Heartbeat) signal. 3.1.3.2 Manchester Encoding The 4-bit wide data is sent to the 10M TX block. The nibbles are converted to a 10Mbps serial NRZI data stream. The 10M PLL locks onto the external clock or internal oscillator and produces a 20MHz clock. This is used to Manchester encode the NRZ data stream. When no data is being transmitted (TXEN is low), the 10M TX block outputs Normal Link Pulses (NLPs) to maintain communications with the remote link partner. 3.1.3.3 10M Transmit Drivers The Manchester encoded data is sent to the analog transmitter where it is shaped and filtered before being driven out as a differential signal across the TXP and TXN outputs. Revision 1.4 (08-23-12) 22 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.1.4 10BASE-T Receive The 10BASE-T receiver gets the Manchester- encoded analog signal from the cable via the magnetics. It recovers the receive clock from the signal and uses this clock to recover the NRZI data stream. This 10M serial data is converted to 4-bit data nibbles which are passed to the controller via MII at a rate of 2.5MHz. This 10M receiver uses the following blocks: (cid:132) Filter and SQUELCH (analog) (cid:132) 10M PLL (analog) (cid:132) RX 10M (digital) (cid:132) MII (digital) 3.1.4.1 10M Receive Input and Squelch The Manchester signal from the cable is fed into the transceiver (on inputs RXP and RXN) via 1:1 ratio magnetics. It is first filtered to reduce any out-of-band noise. It then passes through a SQUELCH circuit. The SQUELCH is a set of amplitude and timing comparators that normally reject differential voltage levels below 300mV and detect and recognize differential voltages above 585mV. 3.1.4.2 Manchester Decoding The output of the SQUELCH goes to the 10M RX block where it is validated as Manchester encoded data. The polarity of the signal is also checked. If the polarity is reversed (local RXP is connected to RXN of the remote partner and vice versa), the condition is identified and corrected. The reversed condition is indicated by the XPOL bit of the Special Control/Status Indications Register. The 10M PLL is locked onto the received Manchester signal, from which the 20MHz cock is generated. Using this clock, the Manchester encoded data is extracted and converted to a 10MHz NRZI data stream. It is then converted from serial to 4-bit wide parallel data. The 10M RX block also detects valid 10Base-T IDLE signals - Normal Link Pulses (NLPs) - to maintain the link. 3.1.4.3 10M Receive Data Across the RMII Interface The 2-bit data nibbles are sent to the RMII block. These data nibbles are valid on the rising edge of the RMII REF_CLK. 3.1.4.4 Jabber Detection Jabber is a condition in which a station transmits for a period of time longer than the maximum permissible packet length, usually due to a fault condition, which results in holding the TXEN input for a long period. Special logic is used to detect the jabber state and abort the transmission to the line within 45ms. Once TXEN is deasserted, the logic resets the jabber condition. As shown in Section 4.2.2, "Basic Status Register," on page50, the Jabber Detect bit indicates that a jabber condition was detected. 3.2 Auto-negotiation The purpose of the auto-negotiation function is to automatically configure the transceiver to the optimum link parameters based on the capabilities of its link partner. Auto-negotiation is a mechanism for exchanging configuration information between two link-partners and automatically selecting the highest performance mode of operation supported by both sides. Auto-negotiation is fully defined in clause 28 of the IEEE 802.3 specification. Once auto-negotiation has completed, information about the resolved link can be passed back to the controller via the Serial Management Interface (SMI). The results of the negotiation process are SMSC LAN8720A/LAN8720Ai 23 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet reflected in the Speed Indication bits of the PHY Special Control/Status Register, as well as in the Auto Negotiation Link Partner Ability Register. The auto-negotiation protocol is a purely physical layer activity and proceeds independently of the MAC controller. The advertised capabilities of the transceiver are stored in the Auto Negotiation Advertisement Register. The default advertised by the transceiver is determined by user-defined on-chip signal options. The following blocks are activated during an Auto-negotiation session: (cid:132) Auto-negotiation (digital) (cid:132) 100M ADC (analog) (cid:132) 100M PLL (analog) (cid:132) 100M equalizer/BLW/clock recovery (DSP) (cid:132) 10M SQUELCH (analog) (cid:132) 10M PLL (analog) (cid:132) 10M Transmitter (analog) When enabled, auto-negotiation is started by the occurrence of one of the following events: (cid:132) Hardware reset (cid:132) Software reset (cid:132) Power-down reset (cid:132) Link status down (cid:132) Setting the Restart Auto-Negotiate bit of the Basic Control Register On detection of one of these events, the transceiver begins auto-negotiation by transmitting bursts of Fast Link Pulses (FLP), which are bursts of link pulses from the 10M transmitter. They are shaped as Normal Link Pulses and can pass uncorrupted down CAT-3 or CAT-5 cable. A Fast Link Pulse Burst consists of up to 33 pulses. The 17 odd-numbered pulses, which are always present, frame the FLP burst. The 16 even-numbered pulses, which may be present or absent, contain the data word being transmitted. Presence of a data pulse represents a “1”, while absence represents a “0”. The data transmitted by an FLP burst is known as a “Link Code Word.” These are defined fully in IEEE 802.3 clause 28. In summary, the transceiver advertises 802.3 compliance in its selector field (the first 5 bits of the Link Code Word). It advertises its technology ability according to the bits set in the Auto Negotiation Advertisement Register. There are 4 possible matches of the technology abilities. In the order of priority these are: (cid:132) 100M Full Duplex (Highest Priority) (cid:132) 100M Half Duplex (cid:132) 10M Full Duplex (cid:132) 10M Half Duplex (Lowest Priority) If the full capabilities of the transceiver are advertised (100M, Full Duplex), and if the link partner is capable of 10M and 100M, then auto-negotiation selects 100M as the highest performance mode. If the link partner is capable of half and full duplex modes, then auto-negotiation selects full duplex as the highest performance operation. Once a capability match has been determined, the link code words are repeated with the acknowledge bit set. Any difference in the main content of the link code words at this time will cause auto-negotiation to re-start. Auto-negotiation will also re-start if not all of the required FLP bursts are received. The capabilities advertised during auto-negotiation by the transceiver are initially determined by the logic levels latched on the MODE[2:0] configuration straps after reset completes. These configuration straps can also be used to disable auto-negotiation on power-up. Refer to Section 3.7.2, "MODE[2:0]: Mode Configuration," on page31 for additional information. Revision 1.4 (08-23-12) 24 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Writing the bits 8 through 5 of the Auto Negotiation Advertisement Register allows software control of the capabilities advertised by the transceiver. Writing the Auto Negotiation Advertisement Register does not automatically re-start auto-negotiation. The Restart Auto-Negotiate bit of the Basic Control Register must be set before the new abilities will be advertised. Auto-negotiation can also be disabled via software by clearing the Auto-Negotiation Enable bit of the Basic Control Register. Note: The device does not support “Next Page” capability. 3.2.1 Parallel Detection If the LAN8720A/LAN8720Ai is connected to a device lacking the ability to auto-negotiate (i.e. no FLPs are detected), it is able to determine the speed of the link based on either 100M MLT-3 symbols or 10M Normal Link Pulses. In this case the link is presumed to be half duplex per the IEEE standard. This ability is known as “Parallel Detection.” This feature ensures interoperability with legacy link partners. If a link is formed via parallel detection, then the Link Partner Auto-Negotiation Able bit of the Auto Negotiation Expansion Register is cleared to indicate that the Link Partner is not capable of auto- negotiation. The controller has access to this information via the management interface. If a fault occurs during parallel detection, the Parallel Detection Fault bit of Link Partner Auto-Negotiation Able is set. Auto Negotiation Link Partner Ability Register is used to store the link partner ability information, which is coded in the received FLPs. If the link partner is not auto-negotiation capable, then the Auto Negotiation Link Partner Ability Register is updated after completion of parallel detection to reflect the speed capability of the link partner. 3.2.2 Restarting Auto-negotiation Auto-negotiation can be restarted at any time by setting the Restart Auto-Negotiate bit of the Basic Control Register. Auto-negotiation will also restart if the link is broken at any time. A broken link is caused by signal loss. This may occur because of a cable break, or because of an interruption in the signal transmitted by the link partner. Auto-negotiation resumes in an attempt to determine the new link configuration. If the management entity re-starts auto-negotiation by setting the Restart Auto-Negotiate bit of the Basic Control Register, the LAN8720A/LAN8720Ai will respond by stopping all transmission/receiving operations. Once the break_link_timer is completed in the Auto-negotiation state-machine (approximately 1200ms), auto-negotiation will re-start. In this case, the link partner will have also dropped the link due to lack of a received signal, so it too will resume auto-negotiation. 3.2.3 Disabling Auto-negotiation Auto-negotiation can be disabled by setting the Auto-Negotiation Enable bit of the Basic Control Register to zero. The device will then force its speed of operation to reflect the information in the Basic Control Register (Speed Select bit and Duplex Mode bit). These bits should be ignored when auto- negotiation is enabled. 3.2.4 Half vs. Full Duplex Half duplex operation relies on the CSMA/CD (Carrier Sense Multiple Access / Collision Detect) protocol to handle network traffic and collisions. In this mode, the carrier sense signal, CRS, responds to both transmit and receive activity. If data is received while the transceiver is transmitting, a collision results. In full duplex mode, the transceiver is able to transmit and receive data simultaneously. In this mode, CRS responds only to receive activity. The CSMA/CD protocol does not apply and collision detection is disabled. SMSC LAN8720A/LAN8720Ai 25 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.3 HP Auto-MDIX Support HP Auto-MDIX facilitates the use of CAT-3 (10BASE-T) or CAT-5 (100BASE-T) media UTP interconnect cable without consideration of interface wiring scheme. If a user plugs in either a direct connect LAN cable, or a cross-over patch cable, as shown in Figure3.4, the device’s Auto-MDIX transceiver is capable of configuring the TXP/TXN and RXP/RXN pins for correct transceiver operation. The internal logic of the device detects the TX and RX pins of the connecting device. Since the RX and TX line pairs are interchangeable, special PCB design considerations are needed to accommodate the symmetrical magnetics and termination of an Auto-MDIX design. The Auto-MDIX function can be disabled via the AMDIXCTRL bit in the Special Control/Status Indications Register. RJ-45 8-pin straight-through RJ-45 8-pin cross-over for for 10BASE-T/100BASE-TX 10BASE-T/100BASE-TX signaling signaling TXP 1 1 TXP TXP 1 1 TXP TXN 2 2 TXN TXN 2 2 TXN RXP 3 3 RXP RXP 3 3 RXP Not Used 4 4 Not Used Not Used 4 4 Not Used Not Used 5 5 Not Used Not Used 5 5 Not Used RXN 6 6 RXN RXN 6 6 RXN Not Used 7 7 Not Used Not Used 7 7 Not Used Not Used 8 8 Not Used Not Used 8 8 Not Used Direct Connect Cable Cross-Over Cable Figure3.4 Direct Cable Connection vs. Cross-over Cable Connection Revision 1.4 (08-23-12) 26 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.4 MAC Interface 3.4.1 RMII The device supports the low pin count Reduced Media Independent Interface (RMII) intended for use between Ethernet transceivers and switch ASICs. Under IEEE 802.3, an MII comprised of 16 pins for data and control is defined. In devices incorporating many MACs or transceiver interfaces such as switches, the number of pins can add significant cost as the port counts increase. RMII reduces this pin count while retaining a management interface (MDIO/MDC) that is identical to MII. The RMII interface has the following characteristics: (cid:132) It is capable of supporting 10Mbps and 100Mbps data rates (cid:132) A single clock reference is used for both transmit and receive (cid:132) It provides independent 2-bit (di-bit) wide transmit and receive data paths (cid:132) It uses LVCMOS signal levels, compatible with common digital CMOS ASIC processes The RMII includes the following interface signals (1 optional): (cid:132) transmit data - TXD[1:0] (cid:132) transmit strobe - TXEN (cid:132) receive data - RXD[1:0] (cid:132) receive error - RXER (Optional) (cid:132) carrier sense - CRS_DV (cid:132) Reference Clock - (RMII references usually define this signal as REF_CLK) 3.4.1.1 CRS_DV - Carrier Sense/Receive Data Valid The CRS_DV is asserted by the device when the receive medium is non-idle. CRS_DV is asserted asynchronously on detection of carrier due to the criteria relevant to the operating mode. In 10BASE- T mode when squelch is passed, or in 100BASE-X mode when 2 non-contiguous zeroes in 10 bits are detected, the carrier is said to be detected. Loss of carrier shall result in the deassertion of CRS_DV synchronous to the cycle of REF_CLK which presents the first di-bit of a nibble onto RXD[1:0] (i.e. CRS_DV is deasserted only on nibble boundaries). If the device has additional bits to be presented on RXD[1:0] following the initial deassertion of CRS_DV, then the device shall assert CRS_DV on cycles of REF_CLK which present the second di-bit of each nibble and de-assert CRS_DV on cycles of REF_CLK which present the first di-bit of a nibble. The result is, starting on nibble boundaries, CRS_DV toggles at 25 MHz in 100Mbps mode and 2.5 MHz in 10Mbps mode when CRS ends before RXDV (i.e. the FIFO still has bits to transfer when the carrier event ends). Therefore, the MAC can accurately recover RXDV and CRS. During a false carrier event, CRS_DV shall remain asserted for the duration of carrier activity. The data on RXD[1:0] is considered valid once CRS_DV is asserted. However, since the assertion of CRS_DV is asynchronous relative to REF_CLK, the data on RXD[1:0] shall be “00” until proper receive signal decoding takes place. 3.4.1.2 Reference Clock (REF_CLK) The RMII REF_CLK is a continuous clock that provides the timing reference for CRS_DV, RXD[1:0], TXEN, TXD[1:0] and RXER. The device uses REF_CLK as the network clock such that no buffering is required on the transmit data path. However, on the receive data path, the receiver recovers the clock from the incoming data stream, and the device uses elasticity buffering to accommodate for differences between the recovered clock and the local REF_CLK. SMSC LAN8720A/LAN8720Ai 27 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.5 Serial Management Interface (SMI) The Serial Management Interface is used to control the device and obtain its status. This interface supports registers 0 through 6 as required by Clause 22 of the 802.3 standard, as well as “vendor- specific” registers 16 to 31 allowed by the specification. Non-supported registers (such as 7 to 15) will be read as hexadecimal “FFFF”. Device registers are detailed in Chapter4, "Register Descriptions," on page47. At the system level, SMI provides 2 signals: MDIO and MDC. The MDC signal is an aperiodic clock provided by the station management controller (SMC). MDIO is a bi-directional data SMI input/output signal that receives serial data (commands) from the controller SMC and sends serial data (status) to the SMC. The minimum time between edges of the MDC is 160 ns. There is no maximum time between edges. The minimum cycle time (time between two consecutive rising or two consecutive falling edges) is 400 ns. These modest timing requirements allow this interface to be easily driven by the I/O port of a microcontroller. The data on the MDIO line is latched on the rising edge of the MDC. The frame structure and timing of the data is shown in Figure3.5 and Figure3.6. The timing relationships of the MDIO signals are further described in Section 5.5.5, "SMI Timing," on page73. Read Cycle MDC ... MDIO 32 1's 0 1 1 0 A4 A3 A2 A1 A0 R4 R3 R2 R1 R0 D15 D14 ... D1 D0 Start of OP Turn Preamble PHY Address Register Address Data Frame Code Around Data To Phy Data From Phy Figure3.5 MDIO Timing and Frame Structure - READ Cycle Write Cycle MDC ... MDIO 32 1's 0 1 0 1 A4 A3 A2 A1 A0 R4 R3 R2 R1 R0 D15 D14 ... D1 D0 Start of OP Turn Preamble PHY Address Register Address Data Frame Code Around Data To Phy Figure3.6 MDIO Timing and Frame Structure - WRITE Cycle Revision 1.4 (08-23-12) 28 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.6 Interrupt Management The device management interface supports an interrupt capability that is not a part of the IEEE 802.3 specification. This interrupt capability generates an active low asynchronous interrupt signal on the nINT output whenever certain events are detected as setup by the Interrupt Mask Register. The device’s interrupt system provides two modes, a Primary Interrupt mode and an Alternative interrupt mode. Both systems will assert the nINT pin low when the corresponding mask bit is set. These modes differ only in how they de-assert the nINT interrupt output. These modes are detailed in the following subsections. Note: The Primary interrupt mode is the default interrupt mode after a power-up or hard reset. The Alternative interrupt mode requires setup after a power-up or hard reset. 3.6.1 Primary Interrupt System The Primary interrupt system is the default interrupt mode (ALTINT bit of the Mode Control/Status Register is “0”). The Primary interrupt system is always selected after power-up or hard reset. In this mode, to set an interrupt, set the corresponding mask bit in the Interrupt Mask Register (see Table3.2). Then when the event to assert nINT is true, the nINT output will be asserted. When the corresponding event to deassert nINT is true, then the nINT will be de-asserted. Table3.2 Interrupt Management Table INTERRUPT SOURCE EVENT TO EVENT TO MASK FLAG INTERRUPT SOURCE ASSERT nINT DE-ASSERT nINT 30.7 29.7 ENERGYON 17.1 ENERGYON Rising 17.1 Falling 17.1 or (Note3.1) Reading register 29 30.6 29.6 Auto-Negotiation 1.5 Auto-Negotiate Rising 1.5 Falling 1.5 or complete Complete Reading register 29 30.5 29.5 Remote Fault 1.4 Remote Fault Rising 1.4 Falling 1.4, or Detected Reading register 1 or Reading register 29 30.4 29.4 Link Down 1.2 Link Status Falling 1.2 Reading register 1 or Reading register 29 30.3 29.3 Auto-Negotiation 5.14 Acknowledge Rising 5.14 Falling 5.14 or LP Acknowledge Read register 29 30.2 29.2 Parallel Detection 6.4 Parallel Rising 6.4 Falling 6.4 or Fault Detection Fault Reading register 6, or Reading register 29 or Re-Auto Negotiate or Link down 30.1 29.1 Auto-Negotiation 6.1 Page Received Rising 6.1 Falling of 6.1 or Page Received Reading register 6, or Reading register 29 Re-Auto Negotiate, or Link Down. Note3.1 If the mask bit is enabled and nINT has been de-asserted while ENERGYON is still high, nINT will assert for 256 ms, approximately one second after ENERGYON goes low when the Cable is unplugged. To prevent an unexpected assertion of nINT, the ENERGYON interrupt mask should always be cleared as part of the ENERGYON interrupt service routine. SMSC LAN8720A/LAN8720Ai 29 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Note: The ENERGYON bit in the Mode Control/Status Register is defaulted to a ‘1’ at the start of the signal acquisition process, therefore the INT7 bit in the Interrupt Mask Register will also read as a ‘1’ at power-up. If no signal is present, then both ENERGYON and INT7 will clear within a few milliseconds. 3.6.2 Alternate Interrupt System The Alternate interrupt system is enabled by setting the ALTINT bit of the Mode Control/Status Register to “1”. In this mode, to set an interrupt, set the corresponding bit of the in the Mask Register 30, (see Table3.3). To Clear an interrupt, either clear the corresponding bit in the Interrupt Mask Register to deassert the nINT output, or clear the interrupt source, and write a ‘1’ to the corresponding Interrupt Source Flag. Writing a ‘1’ to the Interrupt Source Flag will cause the state machine to check the Interrupt Source to determine if the Interrupt Source Flag should clear or stay as a ‘1’. If the Condition to deassert is true, then the Interrupt Source Flag is cleared and nINT is also deasserted. If the Condition to deassert is false, then the Interrupt Source Flag remains set, and the nINT remains asserted. For example, setting the INT7 bit in the Interrupt Mask Register will enable the ENERGYON interrupt. After a cable is plugged in, the ENERGYON bit in the Mode Control/Status Register goes active and nINT will be asserted low. To de-assert the nINT interrupt output, either clear the ENERGYON bit in the Mode Control/Status Register by removing the cable and then writing a ‘1’ to the INT7 bit in the Interrupt Mask Register, OR clear the INT7 mask (bit 7 of the Interrupt Mask Register). Table3.3 Alternative Interrupt System Management Table CONDITION BIT TO INTERRUPT SOURCE EVENT TO TO CLEAR MASK FLAG INTERRUPT SOURCE ASSERT nINT DE-ASSERT nINT 30.7 29.7 ENERGYON 17.1 ENERGYON Rising 17.1 17.1 low 29.7 30.6 29.6 Auto-Negotiation 1.5 Auto-Negotiate Rising 1.5 1.5 low 29.6 complete Complete 30.5 29.5 Remote Fault 1.4 Remote Fault Rising 1.4 1.4 low 29.5 Detected 30.4 29.4 Link Down 1.2 Link Status Falling 1.2 1.2 high 29.4 30.3 29.3 Auto-Negotiation 5.14 Acknowledge Rising 5.14 5.14 low 29.3 LP Acknowledge 30.2 29.2 Parallel 6.4 Parallel Detection Rising 6.4 6.4 low 29.2 Detection Fault Fault 30.1 29.1 Auto-Negotiation 6.1 Page Received Rising 6.1 6.1 low 29.1 Page Received Note: The ENERGYON bit in the Mode Control/Status Register is defaulted to a ‘1’ at the start of the signal acquisition process, therefore the INT7 bit in the Interrupt Mask Register will also read as a ‘1’ at power-up. If no signal is present, then both ENERGYON and INT7 will clear within a few milliseconds. Revision 1.4 (08-23-12) 30 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.7 Configuration Straps Configuration straps allow various features of the device to be automatically configured to user defined values. Configuration straps are latched upon Power-On Reset (POR) and pin reset (nRST). Configuration straps include internal resistors in order to prevent the signal from floating when unconnected. If a particular configuration strap is connected to a load, an external pull-up or pull-down resistor should be used to augment the internal resistor to ensure that it reaches the required voltage level prior to latching. The internal resistor can also be overridden by the addition of an external resistor. Note: The system designer must guarantee that configuration strap pins meet the timing requirements specified in Section 5.5.3, "Power-On nRST & Configuration Strap Timing," on page70. If configuration strap pins are not at the correct voltage level prior to being latched, the device may capture incorrect strap values. Note: When externally pulling configuration straps high, the strap should be tied to VDDIO, except for REGOFF and nINTSEL which should be tied to VDD2A. 3.7.1 PHYAD[0]: PHY Address Configuration The PHYAD0 bit is driven high or low to give each PHY a unique address. This address is latched into an internal register at the end of a hardware reset (default = 0b). In a multi-PHY application (such as a repeater), the controller is able to manage each PHY via the unique address. Each PHY checks each management data frame for a matching address in the relevant bits. When a match is recognized, the PHY responds to that particular frame. The PHY address is also used to seed the scrambler. In a multi-PHY application, this ensures that the scramblers are out of synchronization and disperses the electromagnetic radiation across the frequency spectrum. The device’s SMI address may be configured using hardware configuration to either the value 0 or 1. The user can configure the PHY address using Software Configuration if an address greater than 1 is required. The PHY address can be written (after SMI communication at some address is established) using the PHYAD bits of the Special Modes Register. The PHYAD0 hardware configuration strap is multiplexed with the RXER pin. 3.7.2 MODE[2:0]: Mode Configuration The MODE[2:0] configuration straps control the configuration of the 10/100 digital block. When the nRST pin is deasserted, the register bit values are loaded according to the MODE[2:0] configuration straps. The 10/100 digital block is then configured by the register bit values. When a soft reset occurs via the Soft Reset bit of the Basic Control Register, the configuration of the 10/100 digital block is controlled by the register bit values and the MODE[2:0] configuration straps have no affect. The device’s mode may be configured using the hardware configuration straps as summarized in Table3.4. The user may configure the transceiver mode by writing the SMI registers. SMSC LAN8720A/LAN8720Ai 31 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Table3.4 MODE[2:0] Bus DEFAULT REGISTER BIT VALUES MODE[2:0] MODE DEFINITIONS REGISTER 0 REGISTER 4 [13,12,10,8] [8,7,6,5] 000 10Base-T Half Duplex. Auto-negotiation disabled. 0000 N/A 001 10Base-T Full Duplex. Auto-negotiation disabled. 0001 N/A 010 100Base-TX Half Duplex. Auto-negotiation 1000 N/A disabled. CRS is active during Transmit & Receive. 011 100Base-TX Full Duplex. Auto-negotiation disabled. 1001 N/A CRS is active during Receive. 100 100Base-TX Half Duplex is advertised. Auto- 1100 0100 negotiation enabled. CRS is active during Transmit & Receive. 101 Repeater mode. Auto-negotiation enabled. 1100 0100 100Base-TX Half Duplex is advertised. CRS is active during Receive. 110 Power Down mode. In this mode the transceiver will N/A N/A wake-up in Power-Down mode. The transceiver cannot be used when the MODE[2:0] bits are set to this mode. To exit this mode, the MODE bits in Register 18.7:5(see Section 4.2.9, "Special Modes Register," on page57) must be configured to some other value and a soft reset must be issued. 111 All capable. Auto-negotiation enabled. X10X 1111 The MODE[2:0] hardware configuration pins are multiplexed with other signals as shown in Table3.5. Table3.5 Pin Names for Mode Bits MODE BIT PIN NAME MODE[0] RXD0/MODE0 MODE[1] RXD1/MODE1 MODE[2] CRS_DV/MODE2 3.7.3 REGOFF: Internal +1.2V Regulator Configuration The incorporation of flexPWR technology provides the ability to disable the internal +1.2V regulator. When the regulator is disabled, an external +1.2V must be supplied to the VDDCR pin. Disabling the internal +1.2V regulator makes it possible to reduce total system power, since an external switching regulator with greater efficiency (versus the internal linear regulator) can be used to provide +1.2V to the transceiver circuitry. Note: Because the REGOFF configuration strap shares functionality with the LED1 pin, proper consideration must also be given to the LED polarity. Refer to Section 3.8.1.1, "REGOFF and LED1 Polarity Selection," on page37 for additional information on the relation between REGOFF and the LED1 polarity. Revision 1.4 (08-23-12) 32 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.7.3.1 Disabling the Internal +1.2V Regulator To disable the +1.2V internal regulator, a pull-up strapping resistor should be connected from the REGOFF configuration strap to VDD2A. At power-on, after both VDDIO and VDD2A are within specification, the transceiver will sample REGOFF to determine whether the internal regulator should turn on. If the pin is sampled at a voltage greater than V , then the internal regulator is disabled and IH the system must supply +1.2V to the VDDCR pin. The VDDIO voltage must be at least 80% of the operating voltage level (1.44V when operating at 1.8V, 2.0V when operating at 2.5V, 2.64V when operating at 3.3V) before voltage is applied to VDDCR. As described in Section3.7.3.2, when REGOFF is left floating or connected to VSS, the internal regulator is enabled and the system is not required to supply +1.2V to the VDDCR pin. 3.7.3.2 Enabling the Internal +1.2V Regulator The +1.2V for VDDCR is supplied by the on-chip regulator unless the transceiver is configured for the regulator off mode using the REGOFF configuration strap as described in Section3.7.3.1. By default, the internal +1.2V regulator is enabled when REGOFF is floating (due to the internal pull-down resistor). During power-on, if REGOFF is sampled below V , then the internal +1.2V regulator will turn IL on and operate with power from the VDD2A pin. 3.7.4 nINTSEL: nINT/REFCLKO Configuration The nINTSEL configuration strap is used to select between one of two available modes: REF_CLK In Mode (nINT) and REF_CLK Out Mode. The configured mode determines the function of the nINT/REFCLKO pin. The nINTSEL configuration strap is latched at POR and on the rising edge of the nRST. By default, nINTSEL is configured for nINT mode via the internal pull-up resistor. Table3.6 nINTSEL Configuration STRAP VALUE MODE REF_CLK DESCRIPTION nINTSEL = 0 REF_CLK Out Mode nINT/REFCLKO is the source of REF_CLK. nINTSEL = 1 REF_CLK In Mode nINT/REFCLKO is an active low interrupt output. The REF_CLK is sourced externally and must be driven on the XTAL1/CLKIN pin. The RMII REF_CLK is a continuous clock that provides the timing reference for CRS_DV, RXD[1:0], TXEN, TXD[1:0] and RXER. The device uses REF_CLK as the network clock such that no buffering is required on the transmit data path. However, on the receive data path, the receiver recovers the clock from the incoming data stream. The device uses elasticity buffering to accommodate for differences between the recovered clock and the local REF_CLK. In REF_CLK In Mode, the 50MHz REF_CLK is driven on the XTAL1/CLKIN pin. This is the traditional system configuration when using RMII, and is described in Section3.7.4.1. When configured for REF_CLK Out Mode, the device generates the 50MHz RMII REF_CLK and the nINT interrupt is not available. REF_CLK Out Mode allows a low-cost 25MHz crystal to be used as the reference for REF_CLK. This configuration may result in reduced system cost and is described in Section3.7.4.2. Note: Because the nINTSEL configuration strap shares functionality with the LED2 pin, proper consideration must also be given to the LED polarity. Refer to Section 3.8.1.2, "nINTSEL and LED2 Polarity Selection," on page37 for additional information on the relation between nINTSEL and the LED2 polarity. SMSC LAN8720A/LAN8720Ai 33 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.7.4.1 REF_CLK In Mode In REF_CLK In Mode, the 50MHz REF_CLK is driven on the XTAL1/CLKIN pin. A 50MHz source for REF_CLK must be available external to the device when using this mode. The clock is driven to both the MAC and PHY as shown in Figure3.7. LAN8720A/LAN8720Ai 10/100 PHY 24-QFN MAC RMII RMII MDIO MDC Accepts external nINT 50MHz clock Mag RJ45 TXD[1:0] TXP 2 TXN TXEN RXD[1:0] RXP RXN 2 CRS_DV RXER REF_CLK All RMII signals are synchronous to the supplied XTAL1/CLKIN LED[2:1] clock 2 XTAL2 nRST Interface 50MHz Reference Clock Figure3.7 External 50MHz clock sources the REF_CLK 3.7.4.2 REF_CLK Out Mode To reduce BOM cost, the device includes a feature to generate the RMII REF_CLK signal from a low- cost, 25MHz fundamental crystal. This type of crystal is inexpensive in comparison to 3rd overtone crystals that would normally be required for 50MHz. The MAC must be capable of operating with an external clock to take advantage of this feature as shown in Figure3.8. In order to optimize package size and cost, the REFCLKO pin is multiplexed with the nINT pin. In REF_CLK Out mode, the nINT functionality is disabled to accommodate usage of REFCLKO as a 50MHz clock to the MAC. Note: The REF_CLK Out Mode is not part of the RMII Specification. Timing in this mode is not compliant with the RMII specification. To ensure proper system operation, a timing analysis of the MAC and LAN8720 must be performed. Revision 1.4 (08-23-12) 34 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Note: nINT not available in MAC RMII LAN8720A/LAN8720Ai MDIO this configuration 10/100 PHY MDC Capable of 24-QFN accepting 50MHz TXD[1:0] RMII clock 2 TXEN Mag RJ45 RXD[1:0] TXP 2 TXN CRS_DV RXER RXP REF_CLK RXN REFCLKO XTAL1/CLKIN LED[2:1] 25MHz 2 XTAL2 nRST Interface Figure3.8 Sourcing REF_CLK from a 25MHz Crystal In some system architectures, a 25MHz clock source is available. The device can be used to generate the REF_CLK to the MAC as shown in Figure3.9. It is important to note that in this specific example, only a 25MHz clock can be used (clock cannot be 50MHz). Similar to the 25MHz crystal mode, the nINT function is disabled. SMSC LAN8720A/LAN8720Ai 35 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Note: nINT is not available in LAN8720A/LAN8720Ai this configuration 10/100 PHY 24-QFN MAC RMII RMII MDIO MDC Capable of accepting 50MHz TXD[1:0] Mag RJ45 clock 2 TXP TXEN TXN RXD[1:0] RXP 2 RXN CRS_DV RXER REF_CLK REFCLKO 25MHz XTAL1/CLKIN Clock LED[2:1] 2 XTAL2 nRST Interface Figure3.9 Sourcing REF_CLK from External 25MHz Source Revision 1.4 (08-23-12) 36 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.8 Miscellaneous Functions 3.8.1 LEDs Two LED signals are provided as a convenient means to determine the transceiver's mode of operation. All LED signals are either active high or active low as described in Section 3.8.1.2, "nINTSEL and LED2 Polarity Selection" and Section 3.8.1.1, "REGOFF and LED1 Polarity Selection," on page37. The LED1 output is driven active whenever the device detects a valid link, and blinks when CRS is active (high) indicating activity. The LED2 output is driven active when the operating speed is 100Mbps. This LED will go inactive when the operating speed is 10Mbps or during line isolation. Note: When pulling the LED1 and LED2 pins high, they must be tied to VDD2A, NOT VDDIO. 3.8.1.1 REGOFF and LED1 Polarity Selection The REGOFF configuration strap is shared with the LED1 pin. The LED1 output will automatically change polarity based on the presence of an external pull-up resistor. If the LED1 pin is pulled high to VDD2A by an external pull-up resistor to select a logical high for REGOFF, then the LED1 output will be active low. If the LED1 pin is pulled low by the internal pull-down resistor to select a logical low for REGOFF, the LED1 output will then be an active high output. Figure3.10 details the LED1 polarity for each REGOFF configuration. REGOFF = 1 (Regulator OFF) REGOFF = 0 (Regulator ON) LED output = Active Low LED output = Active High VDD2A LED1/REGOFF 10K ~270 ohms ~270 o hms LED1/REGOFF Figure3.10 LED1/REGOFF Polarity Configuration Note: Refer to Section 3.7.3, "REGOFF: Internal +1.2V Regulator Configuration," on page32 for additional information on the REGOFF configuration strap. 3.8.1.2 nINTSEL and LED2 Polarity Selection The nINTSEL configuration strap is shared with the LED2 pin. The LED2 output will automatically change polarity based on the presence of an external pull-down resistor. If the LED2 pin is pulled high to VDD2A to select a logical high for nINTSEL, then the LED2 output will be active low. If the LED2 SMSC LAN8720A/LAN8720Ai 37 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet pin is pulled low by an external pull-down resistor to select a logical low for nINTSEL, the LED2 output will then be an active high output. Figure3.11 details the LED2 polarity for each nINTSEL configuration. nINTSEL = 1 nINTSEL = 0 LED output = Active Low LED output = Active High VDD2A LED2/nINTSEL 10K ~270 ohms ~270 ohms LED2/nINTSEL Figure3.11 LED2/nINTSEL Polarity Configuration Note: Refer to Section 3.7.4, "nINTSEL: nINT/REFCLKO Configuration," on page33 for additional information on the nINTSEL configuration strap. 3.8.2 Variable Voltage I/O The device’s digital I/O pins are variable voltage, allowing them to take advantage of low power savings from shrinking technologies. These pins can operate from a low I/O voltage of +1.62V up to +3.6V. The applied I/O voltage must maintain its value with a tolerance of ± 10%. Varying the voltage up or down after the transceiver has completed power-on reset can cause errors in the transceiver operation. Refer to Chapter5, "Operational Characteristics," on page63 for additional information. Note: Input signals must not be driven high before power is applied to the device. 3.8.3 Power-Down Modes There are two device power-down modes: General Power-Down Mode and Energy Detect Power- Down Mode. These modes are described in the following subsections. 3.8.3.1 General Power-Down This power-down mode is controlled via the Power Down bit of the Basic Control Register. In this mode, the entire transceiver (except the management interface) is powered-down and remains in this mode as long as the Power Down bit is “1”. When the Power Down bit is cleared, the transceiver powers up and is automatically reset. 3.8.3.2 Energy Detect Power-Down This power-down mode is activated by setting the EDPWRDOWN bit of the Mode Control/Status Register. In this mode, when no energy is present on the line the transceiver is powered down (except for the management interface, the SQUELCH circuit, and the ENERGYON logic). The ENERGYON logic is used to detect the presence of valid energy from 100BASE-TX, 10BASE-T, or Auto-negotiation signals. In this mode, when the ENERGYON bit of the Mode Control/Status Register is low, the transceiver is powered-down and nothing is transmitted. When energy is received via link pulses or packets, the ENERGYON bit goes high and the transceiver powers-up. The device automatically resets into the Revision 1.4 (08-23-12) 38 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet state prior to power-down and asserts the nINT interrupt if the ENERGYON interrupt is enabled in the Interrupt Mask Register. The first and possibly the second packet to activate ENERGYON may be lost. When the EDPWRDOWN bit of the Mode Control/Status Register is low, energy detect power-down is disabled. 3.8.4 Isolate Mode The device data paths may be electrically isolated from the RMII interface by setting the Isolate bit of the Basic Control Register to “1”. In isolation mode, the transceiver does not respond to the TXD, TXEN and TXER inputs, but does respond to management transactions. Isolation provides a means for multiple transceivers to be connected to the same RMII interface without contention. By default, the transceiver is not isolated (on power-up (Isolate=0). 3.8.5 Resets The device provides two forms of reset: Hardware and Software. The device registers are reset by both Hardware and Software resets. Select register bits, indicated as “NASR” in the register definitions, are not cleared by a Software reset. The registers are not reset by the power-down modes described in Section3.8.3. Note: For the first 16us after coming out of reset, the RMII interface will run at 2.5 MHz. After this time, it will switch to 25 MHz if auto-negotiation is enabled. 3.8.5.1 Hardware Reset A Hardware reset is asserted by driving the nRST input pin low. When driven, nRST should be held low for the minimum time detailed in Section 5.5.3, "Power-On nRST & Configuration Strap Timing," on page70 to ensure a proper transceiver reset. During a Hardware reset, an external clock must be supplied to the XTAL1/CLKIN signal. Note: A hardware reset (nRST assertion) is required following power-up. Refer to Section 5.5.3, "Power-On nRST & Configuration Strap Timing," on page70 for additional information. 3.8.5.2 Software Reset A Software reset is activated by setting the Soft Reset bit of the Basic Control Register to “1”. All registers bits, except those indicated as “NASR” in the register definitions, are cleared by a Software reset. The Soft Reset bit is self-clearing. Per the IEEE 802.3u standard, clause 22 (22.2.4.1.1) the reset process will be completed within 0.5s from the setting of this bit. 3.8.6 Carrier Sense The carrier sense (CRS) is output on the CRS_DV pin. CRS is a signal defined by the MII specification in the IEEE 802.3u standard. The device asserts CRS based only on receive activity whenever the transceiver is either in repeater mode or full-duplex mode. Otherwise the transceiver asserts CRS based on either transmit or receive activity. The carrier sense logic uses the encoded, unscrambled data to determine carrier activity status. It activates carrier sense with the detection of 2 non-contiguous zeros within any 10 bit span. Carrier sense terminates if a span of 10 consecutive ones is detected before a /J/K/ Start-of Stream Delimiter pair. If an SSD pair is detected, carrier sense is asserted until either /T/R/ End–of-Stream Delimiter pair or a pair of IDLE symbols is detected. Carrier is negated after the /T/ symbol or the first IDLE. If /T/ is not followed by /R/, then carrier is maintained. Carrier is treated similarly for IDLE followed by some non-IDLE symbol. SMSC LAN8720A/LAN8720Ai 39 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.8.7 Link Integrity Test The device performs the link integrity test as outlined in the IEEE 802.3u (Clause 24-15) Link Monitor state diagram. The link status is multiplexed with the 10Mbps link status to form the Link Status bit in the Basic Status Register and to drive the LINK LED (LED1). The DSP indicates a valid MLT-3 waveform present on the RXP and RXN signals as defined by the ANSI X3.263 TP-PMD standard, to the Link Monitor state-machine, using the internal DATA_VALID signal. When DATA_VALID is asserted, the control logic moves into a Link-Ready state and waits for an enable from the auto-negotiation block. When received, the Link-Up state is entered, and the Transmit and Receive logic blocks become active. Should auto-negotiation be disabled, the link integrity logic moves immediately to the Link-Up state when the DATA_VALID is asserted. To allow the line to stabilize, the link integrity logic will wait a minimum of 330 μsec from the time DATA_VALID is asserted until the Link-Ready state is entered. Should the DATA_VALID input be negated at any time, this logic will immediately negate the Link signal and enter the Link-Down state. When the 10/100 digital block is in 10BASE-T mode, the link status is derived from the 10BASE-T receiver logic. 3.8.8 Loopback Operation The device may be configured for near-end loopback and far loopback. These loopback modes are detailed in the following subsections. 3.8.8.1 Near-end Loopback Near-end loopback mode sends the digital transmit data back out the receive data signals for testing purposes, as indicated by the blue arrows in Figure3.12. The near-end loopback mode is enabled by setting the Loopback bit of the Basic Control Register to “1”. A large percentage of the digital circuitry is operational in near-end loopback mode because data is routed through the PCS and PMA layers into the PMD sublayer before it is looped back. The transmitters are powered down regardless of the state of TXEN. TXD TX 10/100 X CAT-5 Ethernet XFMR RXD RX MAC X Digital Analog SMSC Ethernet Transceiver Figure3.12 Near-end Loopback Block Diagram 3.8.8.2 Far Loopback Far loopback is a special test mode for MDI (analog) loopback as indicated by the blue arrows in Figure3.14. The far loopback mode is enabled by setting the FARLOOPBACK bit of the Mode Control/Status Register to “1”. In this mode, data that is received from the link partner on the MDI is looped back out to the link partner. The digital interface signals on the local MAC interface are isolated. Revision 1.4 (08-23-12) 40 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Far-end system TXD TX 10/100 X Link CAT-5 Ethernet XFMR RXD RX Partner MAC X Digital Analog SMSC Ethernet Transceiver Figure3.13 Far Loopback Block Diagram 3.8.8.3 Connector Loopback The device maintains reliable transmission over very short cables, and can be tested in a connector loopback as shown in Figure3.14. An RJ45 loopback cable can be used to route the transmit signals an the output of the transformer back to the receiver inputs, and this loopback will work at both 10 and 100. 1 10/100 TXD TX 2 3 Ethernet XFMR 4 RXD RX 5 MAC 6 7 Digital Analog 8 SMSC RJ45 Loopback Cable. Created by connecting pin 1 to pin 3 Ethernet Transceiver and connecting pin 2 to pin 6. Figure3.14 Connector Loopback Block Diagram 3.9 Application Diagrams This section provides typical application diagrams for the following: (cid:132) Simplified System Level Application Diagram (cid:132) Power Supply Diagram (1.2V Supplied by Internal Regulator) (cid:132) Power Supply Diagram (1.2V Supplied by External Source) (cid:132) Twisted-Pair Interface Diagram (Single Power Supply) (cid:132) Twisted-Pair Interface Diagram (Dual Power Supplies) SMSC LAN8720A/LAN8720Ai 41 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.9.1 Simplified System Level Application Diagram LAN8720A/LAN8720Ai 10/100 PHY 24-QFN RMII RMII MDIO MDC nINT Mag RJ45 TXP TXN TXD[1:0] 2 RXP TXEN RXN RXD[1:0] 2 RXER XTAL1/CLKIN LED[2:1] 25MHz 2 XTAL2 nRST Interface Figure3.15 Simplified System Level Application Diagram Revision 1.4 (08-23-12) 42 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.9.2 Power Supply Diagram (1.2V Supplied by Internal Regulator) LAN8720A/LAN8720Ai 24-QFN Power Supply 3.3V Ch.2 3.3V Core Logic Circuitry VDDCR Internal VDD2A OUT IN Regulator 1 uF 470 pF CBYPASS VDDDIO VDDIO Ch.1 3.3V VDD1A Supply Circuitry 1.8 - 3.3V CF CBYPASS CBYPASS RBIAS LED1/ REGOFF VSS 12.1k ~270 Ohm Figure3.16 Power Supply Diagram (1.2V Supplied by Internal Regulator) SMSC LAN8720A/LAN8720Ai 43 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.9.3 Power Supply Diagram (1.2V Supplied by External Source) LAN8720A/LAN8720Ai 24-QFN Power Supply 3.3V Ch.2 3.3V Core Logic Circuitry VDDCR VDDCR Internal VDD2A Supply OUTRegulator IN 1.2V 1 uF 470 pF (Disabled) CBYPASS VDDDIO VDDIO Ch.1 3.3V VDD1A Supply Circuitry 1.8 - 3.3V CF CBYPASS CBYPASS RBIAS LED1/ REGOFF VSS 12.1k ~270 Ohm 10k Figure3.17 Power Supply Diagram (1.2V Supplied by External Source) Revision 1.4 (08-23-12) 44 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.9.4 Twisted-Pair Interface Diagram (Single Power Supply) Ferrite LAN8720A/LAN8720Ai bead 24-QFN SPuopwpelry 49.9 Ohm Resistors 3.3V VDD2A CBYPASS VDD1A CBYPASS Magnetics RJ45 TXP 1 2 75 3 4 5 6 TXN 7 8 RXP 75 RXN 1000 pF 3 kV CBYPASS Figure3.18 Twisted-Pair Interface Diagram (Single Power Supply) SMSC LAN8720A/LAN8720Ai 45 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 3.9.5 Twisted-Pair Interface Diagram (Dual Power Supplies) LAN8720A/LAN8720Ai 24-QFN SPuopwpelry 49.9 Ohm Resistors SPuopwpelry 3.3V 2.5V - 3.3V VDD2A CBYPASS VDD1A CBYPASS Magnetics RJ45 TXP 1 2 75 3 4 5 6 TXN 7 8 RXP 75 RXN 1000 pF 3 kV CBYPASS Figure3.19 Twisted-Pair Interface Diagram (Dual Power Supplies) Revision 1.4 (08-23-12) 46 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Chapter 4 Register Descriptions This chapter describes the various control and status registers (CSR’s). All registers follow the IEEE 802.3 (clause 22.2.4) management register set. All functionality and bit definitions comply with these standards. The IEEE 802.3 specified register index (in decimal) is included with each register definition, allowing for addressing of these registers via the Serial Management Interface (SMI) protocol. 4.1 Register Nomenclature Table4.1 describes the register bit attribute notation used throughout this document. Table4.1 Register Bit Types REGISTER BIT TYPE NOTATION REGISTER BIT DESCRIPTION R Read: A register or bit with this attribute can be read. W Read: A register or bit with this attribute can be written. RO Read only: Read only. Writes have no effect. WO Write only: If a register or bit is write-only, reads will return unspecified data. WC Write One to Clear: writing a one clears the value. Writing a zero has no effect WAC Write Anything to Clear: writing anything clears the value. RC Read to Clear: Contents is cleared after the read. Writes have no effect. LL Latch Low: Clear on read of register. LH Latch High: Clear on read of register. SC Self-Clearing: Contents are self-cleared after the being set. Writes of zero have no effect. Contents can be read. SS Self-Setting: Contents are self-setting after being cleared. Writes of one have no effect. Contents can be read. RO/LH Read Only, Latch High: Bits with this attribute will stay high until the bit is read. After it is read, the bit will either remain high if the high condition remains, or will go low if the high condition has been removed. If the bit has not been read, the bit will remain high regardless of a change to the high condition. This mode is used in some Ethernet PHY registers. NASR Not Affected by Software Reset. The state of NASR bits do not change on assertion of a software reset. RESERVED Reserved Field: Reserved fields must be written with zeros to ensure future compatibility. The value of reserved bits is not guaranteed on a read. Many of these register bit notations can be combined. Some examples of this are shown below: (cid:132) R/W: Can be written. Will return current setting on a read. (cid:132) R/WAC: Will return current setting on a read. Writing anything clears the bit. SMSC LAN8720A/LAN8720Ai 47 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 4.2 Control and Status Registers Table4.2 provides a list of supported registers. Register details, including bit definitions, are provided in the proceeding subsections. Table4.2 SMI Register Map REGISTER INDEX (DECIMAL) REGISTER NAME GROUP 0 Basic Control Register Basic 1 Basic Status Register Basic 2 PHY Identifier 1 Extended 3 PHY Identifier 2 Extended 4 Auto-Negotiation Advertisement Register Extended 5 Auto-Negotiation Link Partner Ability Register Extended 6 Auto-Negotiation Expansion Register Extended 17 Mode Control/Status Register Vendor-specific 18 Special Modes Vendor-specific 26 Symbol Error Counter Register Vendor-specific 27 Control / Status Indication Register Vendor-specific 29 Interrupt Source Register Vendor-specific 30 Interrupt Mask Register Vendor-specific 31 PHY Special Control/Status Register Vendor-specific Revision 1.4 (08-23-12) 48 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 4.2.1 Basic Control Register Index (In Decimal): 0 Size: 16 bits BITS DESCRIPTION TYPE DEFAULT 15 Soft Reset R/W 0b 1 = software reset. Bit is self-clearing. When setting this bit do not set other SC bits in this register. The configuration (as described in Section 3.7.2, "MODE[2:0]: Mode Configuration," on page31) is set from the register bit values, and not from the mode pins. 14 Loopback R/W 0b 0 = normal operation 1 = loopback mode 13 Speed Select R/W Note4.1 0 = 10Mbps 1 = 100Mbps Note: Ignored if Auto-negotiation is enabled (0.12 = 1). 12 Auto-Negotiation Enable R/W Note4.1 0 = disable auto-negotiate process 1 = enable auto-negotiate process (overrides 0.13 and 0.8) 11 Power Down R/W 0b 0 = normal operation 1 = General power down mode Note: The Auto-Negotiation Enable must be cleared before setting the Power Down. 10 Isolate R/W 0b 0 = normal operation 1 = electrical isolation of PHY from the RMII 9 Restart Auto-Negotiate R/W 0b 0 = normal operation SC 1 = restart auto-negotiate process Note: Bit is self-clearing. 8 Duplex Mode R/W Note4.1 0 = half duplex 1 = full duplex Note: Ignored if Auto-Negotiation is enabled (0.12 = 1). 7:0 RESERVED RO - Note4.1 The default value of this bit is determined by the MODE[2:0] configuration straps. Refer to Section 3.7.2, "MODE[2:0]: Mode Configuration," on page31 for additional information. SMSC LAN8720A/LAN8720Ai 49 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 4.2.2 Basic Status Register Index (In Decimal): 1 Size: 16 bits BITS DESCRIPTION TYPE DEFAULT 15 100BASE-T4 RO 0b 0 = no T4 ability 1 = T4 able 14 100BASE-TX Full Duplex RO 1b 0 = no TX full duplex ability 1 = TX with full duplex 13 100BASE-TX Half Duplex RO 1b 0 = no TX half duplex ability 1 = TX with half duplex 12 10BASE-T Full Duplex RO 1b 0 = no 10Mbps with full duplex ability 1 = 10Mbps with full duplex 11 10BASE-T Half Duplex RO 1b 0 = no 10Mbps with half duplex ability 1 = 10Mbps with half duplex 10 100BASE-T2 Full Duplex RO 0b 0 = PHY not able to perform full duplex 100BASE-T2 1 = PHY able to perform full duplex 100BASE-T2 9 100BASE-T2 Half Duplex RO 0b 0 = PHY not able to perform half duplex 100BASE-T2 1 = PHY able to perform half duplex 100BASE-T2 8 Extended Status RO 0b 0 = no extended status information in register 15 1 = extended status information in register 15 7:6 RESERVED RO - 5 Auto-Negotiate Complete RO 0b 0 = auto-negotiate process not completed 1 = auto-negotiate process completed 4 Remote Fault RO/LH 0b 1 = remote fault condition detected 0 = no remote fault 3 Auto-Negotiate Ability RO 1b 0 = unable to perform auto-negotiation function 1 = able to perform auto-negotiation function 2 Link Status RO/LL 0b 0 = link is down 1 = link is up 1 Jabber Detect RO/LH 0b 0 = no jabber condition detected 1 = jabber condition detected 0 Extended Capabilities RO 1b 0 = does not support extended capabilities registers 1 = supports extended capabilities registers Revision 1.4 (08-23-12) 50 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 4.2.3 PHY Identifier 1 Register Index (In Decimal): 2 Size: 16 bits BITS DESCRIPTION TYPE DEFAULT 15:0 PHY ID Number R/W 0007h Assigned to the 3rd through 18th bits of the Organizationally Unique Identifier (OUI), respectively. SMSC LAN8720A/LAN8720Ai 51 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 4.2.4 PHY Identifier 2 Register Index (In Decimal): 3 Size: 16 bits BITS DESCRIPTION TYPE DEFAULT 15:10 PHY ID Number R/W 110000b Assigned to the 19th through 24th bits of the OUI. 9:4 Model Number R/W 001111b Six-bit manufacturer’s model number. 3:0 Revision Number R/W Note4.2 Four-bit manufacturer’s revision number. Note4.2 The default value of this field will vary dependant on the silicon revision number. Revision 1.4 (08-23-12) 52 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 4.2.5 Auto Negotiation Advertisement Register Index (In Decimal): 4 Size: 16 bits BITS DESCRIPTION TYPE DEFAULT 15:14 RESERVED RO - 13 Remote Fault R/W 0b 0 = no remote fault 1 = remote fault detected 12 RESERVED RO - 11:10 Pause Operation R/W 00b 00 = No PAUSE 01 = Symmetric PAUSE 10 = Asymmetric PAUSE toward link partner 11 = Advertise support for both Symmetric PAUSE and Asymmetric PAUSE toward local device Note: When both Symmetric PAUSE and Asymmetric PAUSE are set, the device will only be configured to, at most, one of the two settings upon auto-negotiation completion. 9 RESERVED RO - 8 100BASE-TX Full Duplex R/W Note4.3 0 = no TX full duplex ability 1 = TX with full duplex 7 100BASE-TX R/W 1b 0 = no TX ability 1 = TX able 6 10BASE-T Full Duplex R/W Note4.3 0 = no 10Mbps with full duplex ability 1 = 10Mbps with full duplex 5 10BASE-T R/W Note4.3 0 = no 10Mbps ability 1 = 10Mbps able 4:0 Selector Field R/W 00001b 00001 = IEEE 802.3 Note4.3 The default value of this bit is determined by the MODE[2:0] configuration straps. Refer to Section 3.7.2, "MODE[2:0]: Mode Configuration," on page31 for additional information. SMSC LAN8720A/LAN8720Ai 53 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 4.2.6 Auto Negotiation Link Partner Ability Register Index (In Decimal): 5 Size: 16 bits BITS DESCRIPTION TYPE DEFAULT 15 Next Page RO 0b 0 = no next page ability 1 = next page capable Note: This device does not support next page ability. 14 Acknowledge RO 0b 0 = link code word not yet received 1 = link code word received from partner 13 Remote Fault RO 0b 0 = no remote fault 1 = remote fault detected 12:11 RESERVED RO - 10 Pause Operation RO 0b 0 = No PAUSE supported by partner station 1 = PAUSE supported by partner station 9 100BASE-T4 RO 0b 0 = no T4 ability 1 = T4 able Note: This device does not support T4 ability. 8 100BASE-TX Full Duplex RO 0b 0 = no TX full duplex ability 1 = TX with full duplex 7 100BASE-TX RO 0b 0 = no TX ability 1 = TX able 6 10BASE-T Full Duplex RO 0b 0 = no 10Mbps with full duplex ability 1 = 10Mbps with full duplex 5 10BASE-T RO 0b 0 = no 10Mbps ability 1 = 10Mbps able 4:0 Selector Field RO 00001b 00001 = IEEE 802.3 Revision 1.4 (08-23-12) 54 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 4.2.7 Auto Negotiation Expansion Register Index (In Decimal): 6 Size: 16 bits BITS DESCRIPTION TYPE DEFAULT 15:5 RESERVED RO - 4 Parallel Detection Fault RO/LH 0b 0 = no fault detected by parallel detection logic 1 = fault detected by parallel detection logic 3 Link Partner Next Page Able RO 0b 0 = link partner does not have next page ability 1 = link partner has next page ability 2 Next Page Able RO 0b 0 = local device does not have next page ability 1 = local device has next page ability 1 Page Received RO/LH 0b 0 = new page not yet received 1 = new page received 0 Link Partner Auto-Negotiation Able RO 0b 0 = link partner does not have auto-negotiation ability 1 = link partner has auto-negotiation ability SMSC LAN8720A/LAN8720Ai 55 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 4.2.8 Mode Control/Status Register Index (In Decimal): 17 Size: 16 bits BITS DESCRIPTION TYPE DEFAULT 15:14 RESERVED RO - 13 EDPWRDOWN R/W 0b Enable the Energy Detect Power-Down mode: 0 = Energy Detect Power-Down is disabled 1 = Energy Detect Power-Down is enabled 12:10 RESERVED RO - 9 FARLOOPBACK R/W 0b Enables far loopback mode (i.e., all the received packets are sent back simultaneously (in 100BASE-TX only)). This mode works even if the Isolate bit (0.10) is set. 0 = Far loopback mode is disabled 1 = Far loopback mode is enabled Refer to Section 3.8.8.2, "Far Loopback," on page40 for additional information. 8:7 RESERVED RO - 6 ALTINT R/W 0b Alternate Interrupt Mode: 0 = Primary interrupt system enabled (Default) 1 = Alternate interrupt system enabled Refer to Section 3.6, "Interrupt Management," on page29 for additional information. 5:2 RESERVED RO - 1 ENERGYON RO 1b Indicates whether energy is detected. This bit transitions to “0” if no valid energy is detected within 256ms. It is reset to “1” by a hardware reset and is unaffected by a software reset. Refer to Section 3.8.3.2, "Energy Detect Power-Down," on page38 for additional information. 0 RESERVED R/W 0b Revision 1.4 (08-23-12) 56 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 4.2.9 Special Modes Register Index (In Decimal): 18 Size: 16 bits BITS DESCRIPTION TYPE DEFAULT 15 RESERVED RO - 14 RESERVED R/W 1b Write as 1, ignore on read. NASR 13:8 RESERVED RO - 7:5 MODE R/W Note4.4 Transceiver mode of operation. Refer to Section 3.7.2, "MODE[2:0]: Mode NASR Configuration," on page31 for additional details. 4:0 PHYAD R/W Note4.5 PHY Address. The PHY Address is used for the SMI address and for NASR initialization of the Cipher (Scrambler) key. Refer to Section 3.7.1, "PHYAD[0]: PHY Address Configuration," on page31 for additional details. Note4.4 The default value of this field is determined by the MODE[2:0] configuration straps. Refer to Section 3.7.2, "MODE[2:0]: Mode Configuration," on page31 for additional information. Note4.5 The default value of this field is determined by the PHYAD[0] configuration strap. Refer to Section 3.7.1, "PHYAD[0]: PHY Address Configuration," on page31 for additional information. SMSC LAN8720A/LAN8720Ai 57 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 4.2.10 Symbol Error Counter Register Index (In Decimal): 26 Size: 16 bits BITS DESCRIPTION TYPE DEFAULT 15:0 SYM_ERR_CNT RO 0000h The symbol error counter increments whenever an invalid code symbol is received (including IDLE symbols) in 100BASE-TX mode. The counter is incremented only once per packet, even when the received packet contains more than one symbol error. This counter increments up to 65,536 (216) and rolls over to 0 after reaching the maximum value. Note: This register is cleared on reset, but is not cleared by reading the register. This register does not increment in 10BASE-T mode. Revision 1.4 (08-23-12) 58 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 4.2.11 Special Control/Status Indications Register Index (In Decimal): 27 Size: 16 bits BITS DESCRIPTION TYPE DEFAULT 15 AMDIXCTRL R/W 0b HP Auto-MDIX control: 0 = Enable Auto-MDIX 1 = Disable Auto-MDIX (use 27.13 to control channel) 14 RESERVED RO - 13 CH_SELECT R/W 0b Manual channel select: 0 = MDI (TX transmits, RX receives) 1 = MDIX (TX receives, RX transmits) 12 RESERVED RO - 11 SQEOFF R/W 0b Disable the SQE test (Heartbeat): NASR 0 = SQE test is enabled 1 = SQE test is disabled 10:5 RESERVED RO - 4 XPOL RO 0b Polarity state of the 10BASE-T: 0 = Normal polarity 1 = Reversed polarity 3:0 RESERVED RO - SMSC LAN8720A/LAN8720Ai 59 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 4.2.12 Interrupt Source Flag Register Index (In Decimal): 29 Size: 16 bits BITS DESCRIPTION TYPE DEFAULT 15:8 RESERVED RO - 7 INT7 RO/LH 0b 0 = not source of interrupt 1 = ENERGYON generated 6 INT6 RO/LH 0b 0 = not source of interrupt 1 = Auto-Negotiation complete 5 INT5 RO/LH 0b 0 = not source of interrupt 1 = Remote Fault Detected 4 INT4 RO/LH 0b 0 = not source of interrupt 1 = Link Down (link status negated) 3 INT3 RO/LH 0b 0 = not source of interrupt 1 = Auto-Negotiation LP Acknowledge 2 INT2 RO/LH 0b 0 = not source of interrupt 1 = Parallel Detection Fault 1 INT1 RO/LH 0b 0 = not source of interrupt 1 = Auto-Negotiation Page Received 0 RESERVED RO 0b Revision 1.4 (08-23-12) 60 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 4.2.13 Interrupt Mask Register Index (In Decimal): 30 Size: 16 bits BITS DESCRIPTION TYPE DEFAULT 15:8 RESERVED RO - 7:1 Mask Bits R/W 0000000b 0 = interrupt source is masked 1 = interrupt source is enabled Note: Refer to Section 4.2.12, "Interrupt Source Flag Register," on page60 for details on the corresponding interrupt definitions. 0 RESERVED RO - SMSC LAN8720A/LAN8720Ai 61 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 4.2.14 PHY Special Control/Status Register Index (In Decimal): 31 Size: 16 bits BITS DESCRIPTION TYPE DEFAULT 15:13 RESERVED RO - 12 Autodone RO 0b Auto-negotiation done indication: 0 = Auto-negotiation is not done or disabled (or not active) 1 = Auto-negotiation is done 11:5 RESERVED - Write as 0000010b, ignore on read. R/W 0000010b 4:2 Speed Indication RO XXX HCDSPEED value: 001 = 10BASE-T half-duplex 101 = 10BASE-T full-duplex 010 = 100BASE-TX half-duplex 110 = 100BASE-TX full-duplex 1:0 RESERVED RO - Revision 1.4 (08-23-12) 62 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Chapter 5 Operational Characteristics 5.1 Absolute Maximum Ratings* Supply Voltage (VDDIO, VDD1A, VDD2A) (Note5.1). . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to +3.6V Digital Core Supply Voltage (VDDCR) (Note5.1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to +1.5V Ethernet Magnetics Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to +3.6V Positive voltage on signal pins, with respect to ground (Note5.2). . . . . . . . . . . . . . . . . . . . . . . . . .+6V Negative voltage on signal pins, with respect to ground (Note5.3) . . . . . . . . . . . . . . . . . . . . . . . .-0.5V Positive voltage on XTAL1/CLKIN, with respect to ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +4.6V Positive voltage on XTAL2, with respect to ground. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +2.5V Ambient Operating Temperature in Still Air (T ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Note5.40 A Storage Temperature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..-55oC to +150oC Junction to Ambient (θ ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..59.8oC/W JA Junction to Case (θ ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..12.6oC/W JC Lead Temperature Range. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Refer to JEDEC Spec. J-STD-020 HBM ESD Performance per JEDEC JESD22-A114. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Class 3A IEC61000-4-2 Contact Discharge ESD Performance (Note5.5). . . . . . . . . . . . . . . . . . . . . . . . . .+/-8kV IEC61000-4-2 Air-Gap Discharge ESD Performance (Note5.5). . . . . . . . . . . . . . . . . . . . . . . . .+/-15kV Latch-up Performance per EIA/JESD 78 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..+/-150mA Note5.1 When powering this device from laboratory or system power supplies, it is important that the absolute maximum ratings not be exceeded or device failure can result. Some power supplies exhibit voltage spikes on their outputs when AC power is switched on or off. In addition, voltage transients on the AC power line may appear on the DC output. If this possibility exists, it is suggested that a clamp circuit be used. Note5.2 This rating does not apply to the following pins: XTAL1/CLKIN, XTAL2, RBIAS. Note5.3 This rating does not apply to the following pins: RBIAS. Note5.4 0oC to +85oC for extended commercial version, -40oC to +85oC for industrial version. Note5.5 Performed by independent 3rd party test facility. *Stresses exceeding those listed in this section could cause permanent damage to the device. This is a stress rating only. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Functional operation of the device at any condition exceeding those indicated in Section 5.2, "Operating Conditions**", Section 5.1, "Absolute Maximum Ratings*", or any other applicable section of this specification is not implied. Note, device signals are NOT 5 volt tolerant unless specified otherwise. SMSC LAN8720A/LAN8720Ai 63 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 5.2 Operating Conditions** Supply Voltage (VDDIO). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+1.62V to +3.6V Analog Port Supply Voltage (VDD1A, VDD2A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+3.0V to +3.6V Digital Core Supply Voltage (VDDCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+1.14V to +1.26V Ethernet Magnetics Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+2.25V to +3.6V Ambient Operating Temperature in Still Air (T ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Note5.4 A **Proper operation of the device is guaranteed only within the ranges specified in this section. After the device has completed power-up, VDDIO and the magnetics power supply must maintain their voltage level with +/-10%. Varying the voltage greater than +/-10% after the device has completed power-up can cause errors in device operation. Note: Do not drive input signals without power supplied to the device. 5.3 Power Consumption This section details the device power measurements taken over various operating conditions. Unless otherwise noted, all measurements were taken with power supplies at nominal values (VDDIO, VDD1A, VDD2A = 3.3V, VDDCR = 1.2V). See Section 3.8.3, "Power-Down Modes," on page38 for a description of the power down modes. For more information on the REF_CLK modes, see Section 3.7.4, "nINTSEL: nINT/REFCLKO Configuration," on page33. 5.3.1 REF_CLK In Mode Table5.1 Device Only Current Consumption and Power Dissipation (REF_CLK In Mode) VDDA3.3 VDDCR VDDIO TOTAL TOTAL POWER POWER POWER CURRENT POWER POWER PIN GROUP PINS(mA) PIN(mA) PIN(mA) (mA) (mW) Max 28 21 0.6 49 159 Typical 26 19 0.5 45 148 100BASE-TX /W TRAFFIC Min 23 18 0.3 41 96 Note5.6 Max 9.7 13 0.6 24 77 Typical 8.9 12 0.5 22 70 10BASE-T /W TRAFFIC Min 8.3 12 0.3 20 42 Note5.6 Max 4.2 3.0 0.2 7.4 25 ENERGY DETECT POWER Typical 4.1 1.9 0.2 6.2 21 DOWN Min 3.9 1.9 0 5.8 16 Note5.6 Max 0.4 2.8 0.2 3.4 11.2 Typical 0.3 1.8 0.2 2.3 7.6 GENERAL POWER DOWN Min 0.3 1.7 0 2 3.0 Note5.6 Revision 1.4 (08-23-12) 64 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Note: The current at VDDCR is either supplied by the internal regulator from current entering at VDD2A, or from an external 1.2V supply when the internal regulator is disabled. Note: Current measurements do not include power applied to the magnetics or the optional external LEDs. The Ethernet component current is typically 41mA in 100BASE-TX mode and 100mA in 10BASE-T mode, independent of the 2.5V or 3.3V supply rail of the transformer. Note5.6 Calculated with full flexPWR features activated: VDDIO=1.8V & internal regulator disabled. 5.3.2 REF_CLK Out Mode . Table5.2 Device Only Current Consumption and Power Dissipation (REF_CLK Out Mode) VDDA3.3 VDDCR VDDIO TOTAL TOTAL POWER POWER POWER CURRENT POWER POWER PIN GROUP PINS(MA) PIN(MA) PIN(MA) (MA) (MW) Max 28 20 6.3 54 179 Typical 26 19 5.8 50 164 100BASE-T /W TRAFFIC Min 22 15 2.9 39 93 Note5.7 Max 9.9 13 6.4 30 96 Typical 8.8 12 5.6 26 85 10BASE-T /W TRAFFIC Min 7.1 10 3.0 20 41 Note5.7 Max 4.5 2.7 0.3 7.5 25 ENERGY DETECT POWER Typical 4.0 1.5 0.2 5.7 19 DOWN Min 3.9 1.2 0 5.1 15 Note5.7 Max 0.4 2.5 0.2 3.1 10.2 Typical 0.4 1.3 0.2 1.9 6.3 GENERAL POWER DOWN Min 0.4 1.0 0 1.4 2.5 Note5.7 Note: The current at VDDCR is either supplied by the internal regulator from current entering at VDD2A, or from an external 1.2V supply when the internal regulator is disabled. Note: Current measurements do not include power applied to the magnetics or the optional external LEDs. The Ethernet component current is typically 41mA in 100BASE-TX mode and 100mA in 10BASE-T mode, independent of the 2.5V or 3.3V supply rail of the transformer. Note5.7 Calculated with full flexPWR features activated: VDDIO=1.8V & internal regulator disabled. SMSC LAN8720A/LAN8720Ai 65 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 5.4 DC Specifications Table5.3 details the non-variable I/O buffer characteristics. These buffer types do not support variable voltage operation. Table5.4 details the variable voltage I/O buffer characteristics. Typical values are provided for 1.8V, 2.5V, and 3.3V VDDIO cases. Table5.3 Non-Variable I/O Buffer Characteristics PARAMETER SYMBOL MIN TYP MAX UNITS NOTES IS Type Input Buffer Low Input Level V -0.3 V ILI High Input Level V 3.6 V IHI Negative-Going Threshold V 1.01 1.19 1.39 V Schmitt trigger ILT Positive-Going Threshold V 1.39 1.59 1.79 V Schmitt trigger IHT Schmitt Trigger Hysteresis V 336 399 459 mV HYS (V - V ) IHT ILT Input Leakage I -10 10 uA Note5.8 IH (V = VSS or VDDIO) IN Input Capacitance C 2 pF IN O12 Type Buffers Low Output Level V 0.4 V I = 12mA OL OL High Output Level V VDD2A - 0.4 V I = -12mA OH OH ICLK Type Buffer Note5.9 (XTAL1 Input) Low Input Level V -0.3 0.35 V ILI High Input Level V 1.4 VDD2A + 0.4 V IHI Note5.8 This specification applies to all inputs and tri-stated bi-directional pins. Internal pull-down and pull-up resistors add +/- 50uA per-pin (typical). Note5.9 XTAL1/CLKIN can optionally be driven from a 25MHz single-ended clock oscillator. Revision 1.4 (08-23-12) 66 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Table5.4 Variable I/O Buffer Characteristics 1.8V 2.5V 3.3V PARAMETER SYMBOL MIN TYP TYP TYP MAX UNITS NOTES VIS Type Input Buffer Low Input Level V -0.3 V ILI High Input Level V 3.6 V IHI Neg-Going Threshold V 0.64 0.83 1.15 1.41 1.76 V Schmitt trigger ILT Pos-Going Threshold V 0.81 0.99 1.29 1.65 1.90 V Schmitt trigger IHT Schmitt Trigger V 102 158 136 138 288 mV HYS Hysteresis (V - V ) IHT ILT Input Leakage I -10 10 uA Note5.10 IH (V = VSS or VDDIO) IN Input Capacitance C 2 pF IN VO8 Type Buffers Low Output Level V 0.4 V I = 8mA OL OL High Output Level V VDDIO - 0.4 V I = -8mA OH OH VOD8 Type Buffer Low Output Level V 0.4 V I = 8mA OL OL Note5.10 This specification applies to all inputs and tri-stated bi-directional pins. Internal pull-down and pull-up resistors add +/- 50uA per-pin (typical). Table5.5 100BASE-TX Transceiver Characteristics PARAMETER SYMBOL MIN TYP MAX UNITS NOTES Peak Differential Output Voltage High V 950 - 1050 mVpk Note5.11 PPH Peak Differential Output Voltage Low V -950 - -1050 mVpk Note5.11 PPL Signal Amplitude Symmetry V 98 - 102 % Note5.11 SS Signal Rise and Fall Time T 3.0 - 5.0 nS Note5.11 RF Rise and Fall Symmetry T - - 0.5 nS Note5.11 RFS Duty Cycle Distortion D 35 50 65 % Note5.12 CD Overshoot and Undershoot V - - 5 % OS Jitter 1.4 nS Note5.13 Note5.11 Measured at line side of transformer, line replaced by 100Ω (+/- 1%) resistor. Note5.12 Offset from 16nS pulse width at 50% of pulse peak. Note5.13 Measured differentially. SMSC LAN8720A/LAN8720Ai 67 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Table5.6 10BASE-T Transceiver Characteristics PARAMETER SYMBOL MIN TYP MAX UNITS NOTES Transmitter Peak Differential Output Voltage V 2.2 2.5 2.8 V Note5.14 OUT Receiver Differential Squelch Threshold V 300 420 585 mV DS Note5.14 Min/max voltages guaranteed as measured with 100Ω resistive load. 5.5 AC Specifications This section details the various AC timing specifications of the device. Note: The SMI timing adheres to the IEEE 802.3 specification. Refer to the IEEE 802.3 specification for additional timing information. Note: The RMII timing adheres to the RMII Consortium RMII Specification R1.2. 5.5.1 Equivalent Test Load Output timing specifications assume a 25pF equivalent test load, unless otherwise noted, as illustrated in Figure5.1 below. OUTPUT 25 pF Figure5.1 Output Equivalent Test Load Revision 1.4 (08-23-12) 68 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 5.5.2 Power Sequence Timing This diagram illustrates the device power sequencing requirements. The VDDIO, VDD1A, VDD2A and magnetics power supplies can turn on in any order provided they all reach operational levels within the specified time period t . Device power supplies can turn off in any order provided they all reach pon 0 volts within the specified time period p . off t t pon poff VDDIO Magnetics Power VDD1A, VDD2A Figure5.2 Power Sequence Timing Table5.7 Power Sequence Timing Values SYMBOL DESCRIPTION MIN TYP MAX UNITS t Power supply turn on time 50 mS pon t Power supply turn off time 500 mS poff Note: When the internal regulator is disabled, a power-up sequencing relationship exists between VDDCR and the 3.3V power supply. For additional information refer to Section 3.7.3, "REGOFF: Internal +1.2V Regulator Configuration," on page32. SMSC LAN8720A/LAN8720Ai 69 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 5.5.3 Power-On nRST & Configuration Strap Timing This diagram illustrates the nRST reset and configuration strap timing requirements in relation to power-on. A hardware reset (nRST assertion) is required following power-up. For proper operation, nRST must be asserted for no less than t . The nRST pin can be asserted at any time, but must rstia not be deasserted before t after all external power supplies have reached 80% of their nominal purstd operating levels. In order for valid configuration strap values to be read at power-up, the t and t css csh timing constraints must be followed. Refer to Section 3.8.5, "Resets," on page39 for additional information. All External 80% Power Supplies t purstd t t purstv rstia nRST t t css csh Configuration Strap Pins Input t t otaa odad Configuration Strap Pins Output Drive Figure5.3 Power-On nRST & Configuration Strap Timing Table5.8 Power-On nRST & Configuration Strap Timing Values SYMBOL DESCRIPTION MIN TYP MAX UNITS t External power supplies at 80% to nRST deassertion 25 mS purstd t External power supplies at 80% to nRST valid 0 nS purstv t nRST input assertion time 100 μS rstia t Configuration strap pins setup to nRST deassertion 200 nS css t Configuration strap pins hold after nRST deassertion 1 nS csh t Output tri-state after nRST assertion 50 nS otaa t Output drive after nRST deassertion 2 800 nS odad (Note5.15) Note: nRST deassertion must be monotonic. Note: Device configuration straps are latched as a result of nRST assertion. Refer to Section 3.7, "Configuration Straps," on page31 for details. Configuration straps must only be pulled high or low and must not be driven as inputs. Note5.15 20 clock cycles for 25MHz, or 40 clock cycles for 50MHz. Revision 1.4 (08-23-12) 70 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 5.5.4 RMII Interface Timing 5.5.4.1 RMII Timing (REF_CLK Out Mode) The 50MHz REF_CLK OUT timing applies to the case when nINTSEL is pulled-low. In this mode, a 25MHz crystal or clock oscillator must be input on the XTAL1/CLKIN and XTAL2 pins. For more information on REF_CLK Out Mode, see Section 3.7.4.2, "REF_CLK Out Mode," on page34. t clkp t t clkh clkl REFCLKO t t t oval oval ohold RXD[1:0], RXER t ohold t oval CRS_DV t t t t t su ihold su ihold ihold TXD[1:0] t t ihold su TXEN Figure5.4 RMII Timing (REF_CLK Out Mode) Table5.9 RMII Timing Values (REF_CLK Out Mode) SYMBOL DESCRIPTION MIN MAX UNITS NOTES t REFCLKO period 20 ns clkp t REFCLKO high time t *0.4 t *0.6 ns clkh clkp clkp t REFCLKO low time t *0.4 t *0.6 ns clkl clkp clkp t RXD[1:0], RXER, CRS_DV output valid from 5.0 ns Note5.16 oval rising edge of REFCLKO t RXD[1:0], RXER, CRS_DV output hold from 1.4 ns Note5.16 ohold rising edge of REFCLKO t TXD[1:0], TXEN setup time to rising edge of 7.0 ns Note5.16 su REFCLKO t TXD[1:0], TXEN input hold time after rising edge 2.0 ns Note5.16 ihold of REFCLKO Note5.16 Timing was designed for system load between 10 pf and 25 pf. SMSC LAN8720A/LAN8720Ai 71 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 5.5.4.2 RMII Timing (REF_CLK In Mode) The 50MHz REF_CLK IN timing applies to the case when nINTSEL is floated or pulled-high. In this mode, a 50MHz clock must be input on the CLKIN pin. For more information on REF_CLK In Mode, see Section 3.7.4.1, "REF_CLK In Mode," on page34. t clkp t t clkh clkl CLKIN (REF_CLK) t t t oval oval ohold RXD[1:0], RXER t ohold t oval CRS_DV t t t t t su ihold su ihold ihold TXD[1:0] t t ihold su TXEN Figure5.5 RMII Timing (REF_CLK In Mode) Table5.10 RMII Timing Values (REF_CLK In Mode) SYMBOL DESCRIPTION MIN MAX UNITS NOTES t CLKIN period 20 ns clkp t CLKIN high time t *0.35 t *0.65 ns clkh clkp clkp t CLKIN low time t *0.35 t *0.65 ns clkl clkp clkp t RXD[1:0], RXER, CRS_DV output valid from 14.0 ns Note5.17 oval rising edge of CLKIN t RXD[1:0], RXER, CRS_DV output hold from 3.0 ns Note5.17 ohold rising edge of CLKIN t TXD[1:0], TXEN setup time to rising edge of 4.0 ns Note5.17 su CLKIN t TXD[1:0], TXEN input hold time after rising edge 1.5 ns Note5.17 ihold of CLKIN Note5.17 Timing was designed for system load between 10 pf and 25 pf. Revision 1.4 (08-23-12) 72 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 5.5.4.3 RMII CLKIN Requirements Table5.11 RMII CLKIN (REF_CLK) Timing Values PARAMETER MIN TYP MAX UNITS NOTES CLKIN frequency 50 MHz CLKIN Frequency Drift ± 50 ppm CLKIN Duty Cycle 40 60 % CLKIN Jitter 150 psec p-p – not RMS 5.5.5 SMI Timing This section specifies the SMI timing of the device. Please refer to Section 3.5, "Serial Management Interface (SMI)," on page28 for additional details. t clkp t t clkh clkl MDC t t val ohold t ohold MDIO (Data-Out) t t su ihold MDIO (Data-In) Figure5.6 SMI Timing Table5.12 SMI Timing Values SYMBOL DESCRIPTION MIN MAX UNITS NOTES t MDC period 400 ns clkp t MDC high time 160 (80%) ns clkh t MDC low time 160 (80%) ns clkl MDIO (read from PHY) output valid from rising 300 ns t val edge of MDC MDIO (read from PHY) output hold from rising 0 ns t ohold edge of MDC MDIO (write to PHY) setup time to rising edge 10 ns t su of MDC MDIO (write to PHY) input hold time after rising 10 ns t ihold edge of MDC SMSC LAN8720A/LAN8720Ai 73 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet 5.6 Clock Circuit The device can accept either a 25MHz crystal or a 25MHz single-ended clock oscillator (±50ppm) input. If the single-ended clock oscillator method is implemented, XTAL2 should be left unconnected and XTAL1/CLKIN should be driven with a nominal 0-3.3V clock signal. See Table5.13 for the recommended crystal specifications. Table5.13 Crystal Specifications PARAMETER SYMBOL MIN NOM MAX UNITS NOTES Crystal Cut AT, typ Crystal Oscillation Mode Fundamental Mode Crystal Calibration Mode Parallel Resonant Mode Frequency F - 25.000 - MHz fund Frequency Tolerance @ 25oC F - - ±50 PPM Note5.18 tol Frequency Stability Over Temp F - - ±50 PPM Note5.18 temp Frequency Deviation Over Time F - +/-3 to 5 - PPM Note5.19 age Total Allowable PPM Budget - - ±50 PPM Note5.20 Shunt Capacitance C - 7 typ - pF O Load Capacitance C - 20 typ - pF L Drive Level P 300 - - uW W Equivalent Series Resistance R - - 30 Ohm 1 Operating Temperature Range Note5.21 - +85 oC XTAL1/CLKIN Pin Capacitance - 3 typ - pF Note5.22 XTAL2 Pin Capacitance - 3 typ - pF Note5.22 Note5.18 The maximum allowable values for Frequency Tolerance and Frequency Stability are application dependant. Since any particular application must meet the IEEE ±50 PPM Total PPM Budget, the combination of these two values must be approximately ±45 PPM (allowing for aging). Note5.19 Frequency Deviation Over Time is also referred to as Aging. Note5.20 The total deviation for the Transmitter Clock Frequency is specified by IEEE 802.3u as ±100 PPM. Note5.21 0oC for extended commercial version, -40oC for industrial version. Note5.22 This number includes the pad, the bond wire and the lead frame. PCB capacitance is not included in this value. The XTAL1/CLKIN pin, XTAL2 pin and PCB capacitance values are required to accurately calculate the value of the two external load capacitors. The total load capacitance must be equivalent to what the crystal expects to see in the circuit so that the crystal oscillator will operate at 25.000 MHz. Revision 1.4 (08-23-12) 74 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Chapter 6 Package Outline MIN NOMINAL MAX REMARKS A 0.70 0.85 1.00 Overall Package Height A1 0 0.02 0.05 Standoff A2 - - 0.90 Mold Cap Thickness D/E 3.90 4.00 4.10 X/Y Body Size D1/E1 3.55 3.75 3.95 X/Y Mold Cap Size D2/E2 2.40 2.50 2.60 X/Y Exposed Pad Size L 0.30 0.40 0.50 Terminal Length b 0.18 0.25 0.30 Terminal Width k 0.25 - - Terminal to Exposed Pad Clearance e 0.50 BSC Terminal Pitch Notes: 1. All dimensions are in millimeters unless otherwise noted. 2. Dimension “b” applies to plated terminals and is measured between 0.15 and 0.30 mm from the terminal tip. 3. The pin 1 identifier may vary, but is always located within the zone indicated. SMSC LAN8720A/LAN8720Ai 75 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Revision 1.4 (08-23-12) 76 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Note: Standard reel size is 4000 pieces per reel. SMSC LAN8720A/LAN8720Ai 77 Revision 1.4 (08-23-12) DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Chapter 7 Datasheet Revision History Table7.1 Customer Revision History REVISION LEVEL & DATE SECTION/FIGURE/ENTRY CORRECTION Rev. 1.4 Section 4.2.2, "Basic Status Updated definitions of bits 10:8. (08-23-12) Register," on page50 Section 4.2.11, "Special Updated bit 11 definition. Control/Status Indications Register," on page59 Rev. 1.3 Company disclaimer on Removed company address and phone numbers. (03-12-12) page 2 Rev. 1.3 Table5.9, “RMII Timing Updated t maximum value from 10.0ns to oval (04-20-11) Values (REF_CLK Out 5.0ns. Mode),” on page71 Table2.7, “Power Pins,” on Updated VDDCR pin note to include requirement page14 of 1uF and 470pF decoupling capacitors in parallel to ground on the VDDCR pin. Figure3.16 Power Supply Updated diagrams to include 1uF and 470pF Diagram (1.2V Supplied by decoupling capacitors on the VDDCR pin. Internal Regulator) on page43 and Figure3.16 Power Supply Diagram (1.2V Supplied by Internal Regulator) on page43 Rev. 1.2 (11-10-10) Section 5.5.4, "RMII Updated diagrams and tables to include RXER. Interface Timing," on page71 Section 3.7.4.2, "REF_CLK Added timing note in Section 3.7.4.2, "REF_CLK Out Mode," on page34 Out Mode" Section 5.5.4, "RMII Corrected signal names on RMII timing diagrams Interface Timing," on and tables. Updated Table5.9 t , t , t , and oval ohold su page71 t with 10 ns, 1.4 ns, 7.0 ns, and 2.0 ns, ihold respectively. Table5.8, “Power-On nRST Updated t description: “Output drive after odad & Configuration Strap nRST deassertion” Timing Values,” on page70 Rev. 1.1 (04-09-10) Section 5.1, "Absolute Modified “HBM ESD Performance by adding “per Maximum Ratings*" JEDEC JESD22-A114” and changed “+/-5kV” to “Class 3A” Section 5.3, "Power Corrected typo in the current consumption table Consumption," on page64 row title: “100BASE-TX /W TRAFFIC” Section 5.3, "Power Corrected typo in note regarding Ethernet Consumption," on page64 component current: “The Ethernet component current is typically 41mA in 100BASE-TX mode and 100mA in 10BASE-T mode, independent of the 2.5V or 3.3V supply rail of the transformer.” Revision 1.4 (08-23-12) 78 SMSC LAN8720A/LAN8720Ai DATASHEET

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support Datasheet Table7.1 Customer Revision History (continued) REVISION LEVEL & DATE SECTION/FIGURE/ENTRY CORRECTION Table5.3, “Non-Variable I/O Corrected O12 V minimum value to “VDD2A - OH Buffer Characteristics,” on 0.4” page66 Corrected ICLK V maximum value to “0.35” ILI Corrected ICLK V maximum value to “VDD2A + IHI 0.4” Section 5.2, "Operating Added note: “Do not drive input signals without Conditions**," on page64 power supplied to the device.” Section 5.1, "Absolute Corrected IEC61000-4-2 Contact Discharge ESD Maximum Ratings*," on Performance to +/-8kV. page63 Section 4.2.4, "PHY Corrected Model Number default value to Identifier 2 Register," on “001111b”. page52 Section 3.8.8.2, "Far Added far loopback description. Loopback," on page40 Section 4.2.8, "Mode Added FARLOOPBACK (bit 9) description. Control/Status Register," on page56 Rev. 1.0 (12-09-09) Document reworked for clarity and consistency with other SMSC documentation. Rev. 1.0 (04-15-09) Initial Release SMSC LAN8720A/LAN8720Ai 79 Revision 1.4 (08-23-12) DATASHEET

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