MIC2545A/2549A Programmable Current-Limit High-Side Switch General Description Features The MIC2545A and MIC2549A are integrated high-side • 2.7V to 5.5V input power switches optimized for low-loss DC power switching • Adjustable current-limit up to 3A and other power-management applications, including • Reverse current flow blocking advanced configuration and power interface (ACPI). The MIC2545A/49A is a cost-effective, highly-integrated • 90µA typical on-state supply current solution that requires few external components to satisfy • 1µA typical off-state supply current USB and ACPI requirements. • 50mΩ maximum on-resistance Load current management features include a precision, • Open-drain fault flag resistor-programmable output current-limit and a soft-start • Thermal shutdown circuit, which minimizes inrush current when the switch is • Thermal-shutdown output latch (MIC2549A) enabled. Thermal shutdown, along with adjustable current- limit, protects the switch and the attached device. • 2ms (slow) soft-start turn-on, fast turnoff The MIC2545A/49A’s open-drain flag output is used to • Available with active-high or active-low enable indicate current-limiting or thermal shutdown to a local controller. The MIC2549A has an additional internal latch Applications which turns the output off upon thermal shutdown, providing robust fault control. The enable signal is • USB power distribution compatible with both 3V and 5V logic, and is also used as • PCI Bus Power Switching the thermal shutdown latch reset for the MIC2549A. • Notebook PC The MIC2545A and MIC2549A are available in active-high • ACPI power distribution and active-low enable versions in 8-pin DIP, SOIC, and TSSOP packages. • PC card hot swap applications • Inrush current-limiting Data sheets and support documentation can be found on Micrel’s web site at: www.micrel.com. _________________________________________________________________________________________________________________________ Typical Application Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com June 2011 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Ordering Information Part Number Enable Temperature Range Latch Pb-Free Package MIC2545A-1BM Active HIGH –40°C to +85°C No No 8-Pin SOP MIC2545A-1BN Active HIGH –40°C to +85°C No No 8-Pin DIP MIC2545A-1BTS Active HIGH –40°C to +85°C No No 14-Pin TSSOP MIC2545A-2BM Active LOW –40°C to +85°C No No 8-Pin SOP MIC2545A-2BN Active LOW –40°C to +85°C No No 8-Pin DIP MIC2545A-2BTS Active LOW –40°C to +85°C No No 14-Pin TSSOP MIC2545A-1YM Active HIGH –40°C to +85°C No Yes 8-Pin SOP MIC2545A-1YN Active HIGH –40°C to +85°C No Yes 8-Pin DIP MIC2545A-1YTS Active HIGH –40°C to +85°C No Yes 14-Pin TSSOP MIC2545A-2YM Active LOW –40°C to +85°C No Yes 8-Pin SOP MIC2545A-2YN Active LOW –40°C to +85°C No Yes 8-Pin DIP MIC2545A-2YTS Active LOW –40°C to +85°C No Yes 14-Pin TSSOP MIC2549A-1BM Active HIGH –40°C to +85°C Yes No 8-Pin SOP MIC2549A-1BN Active HIGH –40°C to +85°C Yes No 8-Pin DIP MIC2549A-1BTS Active HIGH –40°C to +85°C Yes No 14-Pin TSSOP MIC2549A-2BM Active LOW –40°C to +85°C Yes No 8-Pin SOP MIC2549A-2BN Active LOW –40°C to +85°C Yes No 8-Pin DIP MIC2549A-2BTS Active LOW –40°C to +85°C Yes No 14-Pin TSSOP MIC2549A-1YM Active HIGH –40°C to +85°C Yes Yes 8-Pin SOP MIC2549A-1YN Active HIGH –40°C to +85°C Yes Yes 8-Pin DIP MIC2549A-1YTS Active HIGH –40°C to +85°C Yes Yes 14-Pin TSSOP MIC2549A-2YM Active LOW –40°C to +85°C Yes Yes 8-Pin SOP MIC2549A-2YN Active LOW –40°C to +85°C Yes Yes 8-Pin DIP MIC2549A-2YTS Active LOW –40°C to +85°C Yes Yes 14-Pin TSSOP June 2011 2 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Pin Configuration 8-Pin SOP (M) 8-Pin DIP (N) 14-Pin TSSOP (TS) Pin Description Pin Number Pin Number Pin Name Pin Function SOP, DIP TSSOP Enable (Input): Logic-compatible enable input (−1 version is active high, −2 1 1 EN version is active low). High input >1.8V typical; low input <1.4V typical. Do not float. MIC2549A only: Also resets thermal-shutdown latch. Fault Flag (Output): Active-low, open-drain output. Indicates overcurrent or 2 3 FLG thermal shutdown. MIC2549A only: Latched low on thermal shutdown. 3 5 GND Ground: supply return. Current Limit: Sets current-limit threshold using an external resistor (R ) 4 7 ILIM SET connected to ground. 76.8Ω < R < 459Ω. SET Supply Input: Output MOSFET drain. Also powers internal circuitry. Both IN 5, 7 8, 12 IN pins must be externally connected together. Switch Output: Output MOSFET source. Both OUT pins must be externally 6, 8 10, 14 OUT connected together. 2, 4, 6, 9, NC Not internally connected. 11, 13 June 2011 3 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (V )....................................................+7.0V Supply Voltage (V ).....................................+2.7V to +5.5V IN IN Output Voltage (VOUT).................................................+7.0V Ambient Temperature (TA)..........................–40°C to +85°C Output Current (I ).................................Internally Limited Package Thermal Resistance OUT Enable Input (VEN)...........................................−0.3V to +7V PDIP (θJA)........................................................130°C/W Fault Flag Voltage (VFLG).............................................+7.0V SOIC (θJA)........................................................160°C/W Fault Flag Current (I )..............................................50mA TSSOP (θ )(4)..................................................100°C/W FLG JA Storage Temperature (Ts).........................–65°C to +150°C Current-Limit Set Range(5)..................................0.5A to 3A Junction Temperature (T )........................Internally Limited J Lead Temperature (soldering, 5sec.).........................260°C ESD Rating(3)..............................................................1500V Electrical Characteristics(4) V = +5V; T = 25°C, bold values indicate –40°C to +85°C, unless noted. IN A Symbol Parameter Condition Min. Typ. Max. Units Switch Off, OUT = Open(6) 0.75 5 µA Supply Current 90 125 Switch On, OUT = Open(6) µA 150 V Enable High Transition(6) 2.4 1.6 EN Enable Input Voltage V Enable Low Transition(6) 1.5 0.8 V = V = 2.4V 0.01 1 EN OH(MIN) Enable Input Current µA V = V = 0.8V 0.01 1 EN OL(MAX) Enable Input Capacitance Note 7 1 pF R Switch Resistance I = 500mA 35 50 mΩ DS(ON) OUT I = 0.5A to 3A, V = 1V to 4V(5) 184 230 276 LIMIT OUT Current-Limit Factor V I = 1A to 2.5A, V = 1V to 4V(5) 195 230 264 LIMIT OUT Output Leakage Current Switch Off, V = 0V 1 10 µA OUT t Output Turn-On Delay R = 10Ω, C = 1µF, Figures 1a, 1b 1 2 5 ms ON L L t Output Turn-On Rise Time R = 10Ω, C = 1µF, Figures 1a, 1b 0.75 1.8 4.9 ms R L L t Output Turn-Off Delay R = 10Ω, C = 1µF, Figures 1a, 1b 25 µs OFF L L Notes: 1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating. 3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF. 4. Assumes 4-layer PCB is used. 230 5. Current limit is determined by I = , where R is in Ωs, and 230 is typical current-limit factor in volts. LIMIT SET R SET 6. Off is ≤ 0.8V and on is ≥ 2.4V for the MIC2545A-1 and MIC2549A-1. Off is ≥ 2.4V and on is ≤ 9.8V for the MIC2545A-2 and MIC2549A-2. The enable input has about 100mV of hysteresis. 7. Guaranteed by design but not production tested. June 2011 4 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Electrical Characteristics(4) (Continued) V = +5V; T = 25°C, bold values indicate –40°C to +85°C, unless noted. IN A Symbol Parameter Condition Min. Typ. Max. Units t Output Turn-Off Fall Time R = 10Ω, C = 1µF, Figures 1a, 1b 23 µs F L L T Overtemperature Threshold J Increasing 135 °C Shutdown T Decreasing 120 J Error Flag Off Current V = 5V 0.01 1 µA FLG EN Pulse Reset Width MIC2549A Thermal-Shutdown Latch(7) 1 µs t V to EN Set-Up MIC2549(7), Figure 1c 0 µs SU IN Current-Limit Response Time V = 0V to I = 2A, I = 1A(7) 40 µs OUT OUT SET V Error Flag Output Resistance I = 10mA 4 15 Ω OL FLG Test Circuit Functional Characteristics Test Circuit June 2011 5 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Timing Diagrams Figure 1a. MIC2545A/49A-2 Figure 1b. MIC2545A/49A-1 Figure 1c. Input-to-Enable Setup Timing June 2011 6 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Timing Diagrams (Continued) Figure 2a. MIC2545A-2 Timing: Output is Reset by Toggling EN Figure 2b. MIC2545A-2 Timing June 2011 7 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Typical Characteristics June 2011 8 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Typical Characteristics (Continued) June 2011 9 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Functional Characteristics June 2011 10 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Functional Characteristics (Continued) June 2011 11 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Block Diagram June 2011 12 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Functional Description The current-limit response of the MIC2545A/49A is based on the type of load that is applied to the output The MIC2545A and MIC2549A are high-side N-channel and is defined in three parts: switches available with active-high or active-low enable 1. The first mode of operation is where the device inputs. Fault conditions turn off or inhibit turn-on of the enters a constant-current mode preventing further output transistor and activate the open-drain error flag increases in output current. The value of this current, transistor making it sink current to ground. I , is defined by the value of R as explained LIMIT SET further in this section. Input and Output IN is the power supply connection to the logic circuitry 2. When a short circuit is applied to the output of an enabled device the output current immediately folds and the drain of the output MOSFET. OUT is the source of the output MOSFET. In a typical circuit, current flows back to a value less than ILIMIT called ISHORT. This from IN to OUT toward the load. If V is greater than further protects the load and reduces device power OUT V , current will flow from OUT to IN since the switch is dissipation. Refer to the “Typical Characteristics: IN bidirectional when enabled. The output MOSFET and Output Current vs. Output Voltage” graph for details. driver circuitry are also designed to allow the MOSFET 3. When a load is increased, the output current will source to be externally forced to a higher voltage than proportionally increase up to the current-limit the drain (V > V ) when the switch is disabled. In this threshold, I , as shown in the “Functional OUT IN TH situation, the MIC2545A/49A avoids undesirable current Characteristics: Current-Limit Response” graph. The flow from OUT to IN. Both IN pins must be connected device in this case will supply current slightly higher together, and both OUT pins must be connected than the current-limit set point defined by R . As SET together. the load is increased further the current folds back to I . LIMIT Thermal Shutdown Thermal shutdown shuts off the output MOSFET and The nominal current-limit value, I , is set with an signals the fault flag if the die temperature exceeds LIMIT external resistor between I (Pin 4) and GND (Pin 3). 135°C. 10°C of hysteresis prevents the switch from LIM For a desired current-limit, the value of the external set turning on until the die temperature drops to 125°C. resistor is given by: Overtemperature detection functions only when the switch is enabled. The MIC2549A features an internal latch which causes ⎛ 230 ⎞ R =⎜ ⎟ the part to remain off after thermal shutdown until a reset SET ⎜ ⎟ ⎝ILIMIT ⎠ pulse is provided via the enable pin (pin1).While in current-limit, the thermal shutdown latch prevents on/off cycling of the output. Refer to Figure 2 for timing where: diagram. The flag remains low until reset. Enable Input 76.8Ω < R < 459Ω SET EN must be driven logic high or logic low, or be pulled high or low for a clearly defined input. Floating the input Refer to the “Typical Characteristics: Current-Limit vs may cause unpredictable operation. EN should not be R ” graph for more details. SET allowed to go negative with respect to GND. Current through R increases with output current. The SET voltage across R could be monitored with a high- Current-Limit Operation SET impedance comparator to provide an indication of output The current limit is user adjustable with an external set current. R should be between 76.8Ω and 459Ω (1% resistor. Current limiting in the range of 500mA to 3A is SET resister value). available with a set point accuracy of better than ±30% (±20% for ISET 1 to 2.5A). The current-limit circuit Fault Flag prevents damage to the output MOSFET and external FLG is an N-channel, open-drain MOSFET output. The load. fault-flag is active (low) for current-limit or thermal shutdown conditions. The flag output MOSFET is capable of sinking a 10mA load to typically 100mV above ground. For applications with V = 3.6V, it is IN recommended that flag current be limited to 5mA or less. June 2011 13 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Application Information To relate this to junction temperature, the following equation can be used: Supply Filtering A 0.1µF to 1µF bypass capacitor from IN to GND, T = P × θ + T J D JA A located near the MIC2545A and MIC2549A, is strongly recommended to control supply transients. Without a where: bypass capacitor, an output short may cause sufficient ringing on the input (from supply lead inductance) to TJ = Junction temperature damage internal control circuitry. T = Ambient temperature A Input transients must not exceed the absolute maximum θ = The thermal resistance of the package JA supply voltage (V (max) = 6V) even for a short IN duration. Transient Overcurrent Filter The inrush current from the connection of a heavy capacitive load may cause the fault flag to fall for 10µs to 200µs while the switch is in a constant-current mode, charging the capacitance. Adding an optional series resistor-capacitor (R ) in parallel with RSET, as SET2 shown in Figure 4, allows the transient current-limit to be set to a different value than steady state. A typical USB hot-plug inrush is 2A to 3A for 10µs to 20µs. If R is SET 435Ω (530mA), an R of 88Ω (2.5A) and C of 1µF SET2 SET (RC ≈ 90µs) allows transient surge of 3A to pass for 90µs without tripping the overcurrent flag (FLG). USB Power Dissipations Figure 3. Supply Bypassing The MIC2545A is ideal for meeting USB power distribution requirements. Figure 7 depicts a USB Host application. R should be set to a value providing a Power Dissipation SET current-limit >500mA. The accurate current-limit of the The device's junction temperature depends on several MIC2545A will reduce power supply current factors such as the load, PCB layout, ambient requirements. Also, fast reaction to short-circuit faults temperature, and package type. Equations that can be prevent voltage droop in mobile PC applications. used to calculate power dissipation and junction temperature are found below. Printed Circuit Board Hot-Plug Calculation of power dissipation can be accomplished by The MIC2545A/49A is an ideal inrush current-limiter the following equation: suitable for hot-plug applications. Due to the integrated charge pump, the MIC2545A/49A presents a high impedance when off and slowly becomes a low P = R × (I )2 D DS(ON) OUT impedance as it turns on. This “soft start” feature effectively isolates power supplies from highly-capacitive loads by reducing inrush current during hot-plug events. Figure 5 shows how the MIC2545A may be used in a hot-plug application. June 2011 14 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Figure 4. USB Host Application Figure 5. Hot-Plug Application June 2011 15 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Package Information 8-Pin DIP (N) June 2011 16 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Package Information (Continued) 8-Pin SOIC (M) June 2011 17 M9999-062711-A

Micrel, Inc. MIC2545A/2549A Package Information (Continued) 14-Pin TSSOP (TS) MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry, specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2004 Micrel, Incorporated. June 2011 18 M9999-062711-A

Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: M icrel: MIC2549A-1YM TR MIC2549A-1YTS TR M icrochip: MIC2545A-1YN MIC2545A-2YN MIC2549A-1YM MIC2545A-1YM MIC2545A-2YM MIC2549A-1YN MIC2549A- 2YTS MIC2549A-2YM MIC2549A-1YTS MIC2545A-1YTS MIC2549A-2YN MIC2549A-1YTS-TR MIC2549A-2YM-TR MIC2545A-2YTS-TR MIC2549A-1YM-TR MIC2549A-2YTS-TR MIC2545A-1YTS-TR MIC2545A-1YM-TR