LTC1387 Single 5V RS232/RS485 Multiprotocol Transceiver FEATURES DESCRIPTIOU n Two RS232 Transceivers or One RS485 Transceiver The LTC®1387 is a low power reconfigurable CMOS bidi- n Operates from a Single 5V Supply rectional transceiver. It can be configured as an RS485 n Guaranteed Receiver Output with Inputs differential port or as two RS232 single-ended ports. An Floating or Shorted to Ground onboard charge pump uses four 0.1m F capacitors to n Logic Selectable Fast/Slow RS485 Driver Slew Rate generate boosted positive and negative supplies, allowing n Low Supply Current: 7mA Typical the RS232 drivers to meet – 5V output swing require- n 5m A Supply Current in Shutdown ments with only a single 5V supply. A shutdown mode n Self-Testing Capability in Loopback Mode reduces the I supply current to 5m A. CC n Separate Driver and Receiver Enable Controls The RS232 transceivers are in full compliance with RS232 n Driver Maintains High Impedance in Three-State, specification. The RS485 transceiver is in full compliance Shutdown or with Power Off with RS485 and RS422 specifications. The RS485 re- n Receiver Inputs Can Withstand – 25V ceiver assumes a known output state when the inputs are floating or shorted to ground. All interface drivers feature APPLICATIOUNS short-circuit and thermal shutdown protection. An enable pin allows RS485 driver outputs to be forced into high n Point-of-Sale Terminals impedance which is maintained even when the outputs are n Software Selectable Multiprotocol Interface Ports forced beyond supply rails or the power is off. A loop back n Low Power RS485/RS422/RS232/EIA562 Interface mode allows the driver outputs to be connected back to the nCable Repeaters receiver inputs for diagnostic self-test. n Level Translators The LTC1387 is available in 20-pin plastic SSOP and SW packages. , LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATIOU 2 1 20 19 19 20 1 2 3 3 LTC1387 LTC1387 18 VCC2 VCC1 18 5V 5V 4 4 17 RS485 INTERFACE 17 RECOUT 5 5 RECOUT 120W 120W 6 6 15 15 DR IN 7 4000-FT 24-GAUGE TWISTED PAIR 7 DR IN SLEW 14 14 SLEW DR ENABLE 9 8 5V 5V 8 9 DR ENABLE 5V 12 13 5V 5V 13 12 5V 11 10 10 11 ALL CAPACITORS: 0.1m F MONOLITHIC CERAMIC TYPE LTC1387 • TA01 1

LTC1387 ABSOLUTE WAXIWUW RATIUGS PACKAGE/ORDER IUFORWATIOU (Note 1) Supply Voltage (V )............................................. 6.5V ORDER PART CC TOP VIEW Input Voltage NUMBER C1+ 1 20 C2+ Drivers ................................... –0.3V to (V + 0.3V) CC C1– 2 19 C2– Receivers ............................................. –25V to 25V LTC1387CG VDD 3 18 VCC 485/232, ON, DXEN LTC1387CSW A 4 17 RA RXEN, SLEW........................... –0.3V to (VCC + 0.3V) B 5 16 RB LTC1387IG Output Voltage Y 6 15 DY LTC1387ISW Drivers ................................................. –18V to 18V Z 7 14 DZ/SLEW Receivers ............................... –0.3V to (V + 0.3V) 485/232 8 13 ON CC Short-Circuit Duration DXEN 9 12 RXEN Output........................................................ Indefinite GND 10 11 VEE V , V , C1+, C1–, C2+, C2–.......................... 30 sec G PACKAGE SW PACKAGE DD EE 20-LEAD PLASTIC SSOP 20-LEAD PLASTIC SO Operating Temperature Range LTC1387C.............................................. 0(cid:176) C to 70(cid:176) C TJMAX = 125(cid:176)C, q JA = 120(cid:176)C/W (G) LTC1387I ...........................................–40(cid:176) C to 85(cid:176) C TJMAX = 125(cid:176)C, q JA = 75(cid:176)C/W (SW) Storage Temperature Range................ –65(cid:176) C to 150(cid:176) C Lead Temperature (Soldering, 10 sec)................ 300(cid:176) C Consult factory for Military grade parts. DC ELECTRICAL CHARACTERISTICS T = 25(cid:176) C, V = 5V, C1 = C2 = C3 = C4 = 0.1m F (Notes 2, 3), unless otherwise noted. A CC SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS RS485 Driver (485/232 = High, ON = DXEN = High) V Differential Driver Output Voltage (Unloaded) I = 0 l 6 V OD1 O V Differential Driver Output Voltage (With Load) Figure 1, R = 50W (RS422) l 2.0 6 V OD2 Figure 1, R = 27W (RS485) l 1.5 6 V D V Change in Magnitude of Driver Differential Figure 1, R = 27W or R = 50W l 0.2 V OD Output Voltage for Complementary Output States V Driver Common Mode Output Voltage Figure 1, R = 27W or R = 50W l 3 V OC D‰ V ‰ Change in Magnitude of Driver Common Mode Figure 1, R = 27W or R = 50W l 0.2 V OC Output Voltage for Complementary Output States I Driver Short-Circuit Current V = –7V, 12V; V = High l 35 250 mA OSD O O V = –7V, 12V; V = Low (Note 4) l 10 250 mA O O I Three-State Output Current (Y, Z) –7V £ V £ 12V – 5 500 m A OZD O RS232 Driver (485/232 = Low, ON = DXEN = High) V Output Voltage Swing Figure 4, R = 3k, Positive l 5 6.5 V O L Figure 4, R = 3k, Negative l –5 –6.5 V L I Output Short-Circuit Current V = 0V l – 17 – 60 mA OSD O Driver Inputs and Control Inputs VIH Input High Voltage DY, DZ, DXEN, RXEN, ON, 485/232, SLEW l 2 V VIL Input Low Voltage DY, DZ, DXEN, RXEN, ON, 485/232, SLEW l 0.8 V IIN Input Current DY, DZ, DXEN, RXEN, ON, 485/232 l – 0.1 – 10 m A SLEW (Note 5) l 5 15 m A 2

LTC1387 DC ELECTRICAL CHARACTERISTICS T = 25(cid:176) C, V = 5V, C1 = C2 = C3 = C4 = 0.1m F (Notes 2, 3), unless otherwise noted. A CC SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS RS485 Receiver (485/232 = High, ON = RXEN = High) V Differential Input Threshold Voltage –7V £ V £ 12V l –0.20 0.20 V TH CM D V Input Hysteresis V = 0V 40 mV TH CM I Input Current (A, B) V = 12V l 1 mA IN IN V = –7V l –0.8 mA IN R Input Resistance –7V £ V £ 12V l 12 24 kW IN IN RS232 Receiver (485/232 = Low, ON = RXEN = High) V Receiver Input Voltage Threshold Input Low Threshold l 0.8 V TH Input High Threshold l 2.4 V D V Receiver Input Hysteresis 0.6 V TH R Receiver Input Resistance V = – 10V 3 5 7 kW IN IN Receiver Output (ON = RXEN = High) V Receiver Output High Voltage I = –3mA, V = 0V, 485/232 = Low l 3.5 4.6 V OH O IN V Receiver Output Low Voltage I = 3mA, V = 3V, 485/232 = Low l 0.2 0.4 V OL O IN I Short-Circuit Current 0V £ V £ V l 7 85 mA OSR O CC I Three-State Output Current RXEN = 0V l – 0.1 – 10 m A OZR Power Supply Generator V V Output Voltage No Load, ON = DXEN = RXEN = High 8 V DD DD I = –5mA, ON = DXEN = RXEN = High 7 V DD V V Output Voltage No Load, ON = DXEN = RXEN = High –7.7 V EE EE I = 5mA, ON = DXEN = RXEN = High –7.0 V EE Power Supply I V Supply Current No Load, ON = DXEN = RXEN = High l 7 25 mA CC CC Shutdown, ON = DXEN = RXEN = 0V l 5 100 m A AC ELECTRICAL CHARACTERISTICS T = 25(cid:176) C, V = 5V, C1 = C2 = C3 = C4 = 0.1m F (Notes 2, 3), unless otherwise noted. A CC SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS RS232 Mode (ON = DXEN = RXEN = High, 485/232 = Low) SR Slew Rate Figure 4, R = 3k, C = 15pF l 30 V/m s L L Figure 4, R = 3k, C = 1000pF l 4 V/m s L L t Transition Time Figure 4, R = 3k, C = 2500pF l 0.22 1.9 3.1 m s T L L t Driver Input to Output Figures 4, 10, R = 3k, C = 15pF l 0.6 4 m s PLH L L t Driver Input to Output Figures 4, 10, R = 3k, C = 15pF l 0.6 4 m s PHL L L t Receiver Input to Output Figures 5, 11 l 0.3 6 m s PLH t Receiver Input to Output Figures 5, 11 l 0.4 6 m s PHL RS485 Mode (Fast Slew Rate, ON = DXEN = High, 485/232 = High, SLEW = High) t Driver Input to Output Figures 2, 7, R = 54W , C = 100pF l 15 40 70 ns PLH L L t Driver Input to Output Figures 2, 7, R = 54W , C = 100pF l 15 40 70 ns PHL L L t Driver Output to Output Figures 2, 7, R = 54W , C = 100pF l 5 15 ns SKEW L L t, t Driver Rise or Fall Time Figures 2, 7, R = 54W , C = 100pF l 3 15 40 ns r f L L 3

LTC1387 AC ELECTRICAL CHARACTERISTICS T = 25(cid:176) C, V = 5V, C1 = C2 = C3 = C4 = 0.1m F (Notes 2, 3), unless otherwise noted. A CC SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS RS485 Mode (Fast Slew Rate, ON = DXEN = High, 485/232 = High, SLEW = High) t Driver Enable to Output Low Figures 3, 8, C = 100pF, S1 Closed l 50 90 ns ZL L t Driver Enable to Output High Figures 3, 8, C = 100pF, S2 Closed l 50 90 ns ZH L t Driver Disable from Low Figures 3, 8, C = 15pF, S1 Closed l 50 90 ns LZ L t Driver Disable from High Figures 3, 8, C = 15pF, S2 Closed l 60 90 ns HZ L RS485 Mode (Slow Slew Rate, ON = DXEN = High, 485/232 = High, SLEW = Low) t Driver Input to Output Figures 2, 7, R = 54W , C = 100pF l 100 700 1500 ns PLH L L t Driver Input to Output Figures 2, 7, R = 54W , C = 100pF l 100 700 1500 ns PHL L L t Driver Output to Output Figures 2, 7, R = 54W , C = 100pF l 200 750 ns SKEW L L t, t Driver Rise or Fall Time Figures 2, 7, R = 54W , C = 100pF l 150 300 1500 ns r f L L t Driver Enable to Output Low Figures 3, 8, C = 100pF, S1 Closed l 600 1500 ns ZL L t Driver Enable to Output High Figures 3, 8, C = 100pF, S2 Closed l 600 1500 ns ZH L t Driver Disable from Low Figures 3, 8, C = 15pF, S1 Closed l 100 200 ns LZ L t Driver Disable from High Figures 3, 8, C = 15pF, S2 Closed l 100 200 ns HZ L RS485 Mode (ON = RXEN = High, 485/232 = High) t Receiver Input to Output Figures 2, 9, R = 54W , C = 100pF l 20 70 140 ns PLH L L t Receiver Input to Output Figures 2, 9, R = 54W , C = 100pF l 20 70 140 ns PHL L L t Differential Receiver Skew, ‰ t – t ‰ Figures 2, 9, R = 54W , C = 100pF 10 ns SKEW PLH PHL L L Receiver Output Enable/Disable (ON = High) t Receiver Enable to Output Low Figures 6, 12, C = 15pF, S1 Closed l 40 90 ns ZL L t Receiver Enable to Output High Figures 6, 12, C = 15pF, S2 Closed l 40 90 ns ZH L t Receiver Disable from Low Figures 6, 12, C = 15pF, S1 Closed l 40 90 ns LZ L t Receiver Disable from High Figures 6, 12, C = 15pF, S2 Closed l 40 90 ns HZ L The l denotes specifications which apply over the full operating Note 3: All typicals are given at V = 5V, C1 = C2 = C3 = C4 = 0.1m F CC temperature range. and T = 25(cid:176) C. A Note 1: Absolute Maximum Ratings are those values beyond which the life Note 4: Short-circuit current for RS485 driver output low state folds back of the device may be impaired. above V . Peak current occurs around V = 3V. CC O Note 2: All currents into device pins are positive; all currents out of device Note 5: SLEW includes an internal pull-up in RS485 mode. pins are negative. All voltages are referenced to device ground unless otherwise specified. PIUN FUUNCTIOUNS C1+ (Pin 1): Commutating Capacitor C1 Positive Terminal. B (Pin 5): Receiver Input B. Inverting input of RS232 Requires an external 0.1m F capacitor between Pins 1 and 2. receiver B in RS232 mode; noninverting RS485 receiver C1– (Pin 2): Commutating Capacitor C1 Negative Terminal. input in RS485 mode. Y (Pin 6): Driver Output Y. Inverting RS232 driver Y output V (Pin 3): Charge Pump Positive Supply Output. DD Requires an external 0.1m F capacitor to ground. in RS232 mode; inverting RS485 driver output in RS485 mode. A (Pin 4): Receiver Input A. Inverting input of RS232 Z (Pin 7): Driver Output Z. Inverting RS232 driver Z output receiver A in RS232 mode; inverting RS485 receiver input in RS232 mode; noninverting RS485 driver output in in RS485 mode. RS485 mode. 4

LTC1387 PIU FUU CTIOU S 485/232 (Pin 8): Interface Mode Select Input. A low logic be configured for one-, two- or three-wire control: one- input enables two RS232 drivers and two RS232 receiv- wire mode – all three inputs connected together; two-wire ers. A high input enables the RS485 driver and the RS485 mode – inputs ON and RXEN connected to one wire, DXEN receiver. a separate wire; three-wire mode – separate wires to each input. See the Function Tables. DXEN (Pin 9): Driver Enable Input. A high logic input enables the drivers and a low logic input disables the D /SLEW (Pin 14): Driver Z or Slew Input. In RS232 Z drivers. When disabled, all driver outputs are in high mode, this pin is the driver Z input. In RS485 mode, this impedance pin controls the slew rate of the RS485 driver. With the SLEW pin high, the RS485 driver runs at maximum (fast) GND (Pin 10): Ground. slew rate and can transmit signals up to 5MBd. With the V (Pin 11): Charge Pump Negative Supply Output. EE SLEW pin low, the RS485 driver runs with reduced (slow) Requires an external 0.1m F capacitor to ground. slew rate to control reflections with improperly terminated RXEN (Pin 12): Receiver Enable Input. A high logic input cables. In slow mode, the RS485 driver can support data enables the receivers and a low logic input disables the rates up to 150kBd. This SLEW pin has internal 5m A pull- receivers. When disabled, all receiver outputs are in high up during RS485 mode. impedance. D (Pin 15): Driver Y Input. Input Y in RS232 mode; the Y ON (Pin 13): A high logic level at ON input keeps the charge differential driver input in RS485 mode. pump active regardless of the state of the DXEN and RXEN R (Pin 16): Receiver B Output. Output B in RS232 mode; B inputs. When the charge pump is active, the drivers and output is high impedance in RS485 mode. receivers can be enabled or disabled without waiting for charge pump stabilization time (typically 100m s with 0.1m F RA (Pin 17): Receiver A Output. Output A in RS232 mode; the differential receiver output in RS485 mode. capacitors). A low logic state at the ON, DXEN and RXEN inputs will put the transceiver and charge pump in shut- V (Pin 18): Positive Supply. 4.75V £ V £ 5.25V. CC CC down mode and reduces I to 5m A. Whenever the trans- Requires an external 0.1m F bypass capacitor to ground. CC ceiver is activated from shutdown, the charge pump C2–(Pin 19): Commutating Capacitor C2 Negative Termi- should be allowed to stabilize before data transmission. nal. Requires an external 0.1m F capacitor between Pins 19 When DXEN and RXEN are high and ON is low, the charge and 20. pump, drivers and receivers are all active and the driver C2+ (Pin 20): Commutating Capacitor C2 Positive outputs are internally looped back to the inputs of the Terminal. receiver. The three control inputs ON, DXEN and RXEN can 5

LTC1387 FUU CTIOU TABLES Select Modes SELECT INPUTS RECEIVER DRIVER CHARGE PUMP LOOPBACK COMMENTS ON RXEN DXEN 485/232 RXA RXB DXY DXZ 1 0 0 0 Z Z Z Z ON OFF RS232 Mode, DX and RX Off 1 0 1 0 Z Z ON ON ON OFF RS232 Mode, DXY and DXZ On, RX Off 1 1 0 0 ON ON Z Z ON OFF RS232 Mode, DX Off, RXA and RXB On 1 1 1 0 ON ON ON ON ON OFF RS232 Mode, DXY and DXZ On, RXA and RXB On 0 0 1 0 Z Z ON Z ON OFF RS232 Mode, DXY On, DXZ Off, RX Off 0 1 0 0 Z ON ON Z ON OFF RS232 Mode, DXY On, DXZ Off, RXA Off, RXB On 0 1 1 0 ON ON ON ON ON ON RS232 Loopback Mode, DXY and DXZ On, RXA and RXB On 0 0 0 X Z Z Z Z OFF OFF Shutdown, RS485 R IN 1 0 0 1 Z Z Z Z ON OFF RS485 Mode, DX and RX Off X 0 1 1 Z Z ON ON ON OFF RS485 Mode, DX On, RX Off X 1 0 1 ON Z Z Z ON OFF RS485 Mode, DX Off, RX On 1 1 1 1 ON Z ON ON ON OFF RS485 Mode, DX On, RX On 0 1 1 1 ON Z ON ON ON ON RS485 Loopback Mode, DX On, RX On RS232 Driver Mode RS485 Driver Slew Rate INPUTS OUTPUTS INPUTS OUTPUTS SELECTED 485/232 D CONDITIONS Y, Z DXEN 485/232 SLEW SLEW RATE YES 0 0 No Fault 1 1 1 0 Slow YES 0 1 No Fault 0 1 1 1 Fast YES 0 X Thermal Fault Z 0 1 X Z NO 0 X X Z RS485 Driver Mode RS232 Receiver Mode INPUTS OUTPUTS DXEN 485/232 D CONDITIONS Z Y INPUTS OUTPUTS SELECTED 485/232 A, B R , R 1 1 0 No Fault 0 1 A B YES 0 0 1 1 1 1 No Fault 1 0 YES 0 1 0 1 1 X Thermal Fault Z Z YES 0 Inputs Open 1 0 1 X X Z Z NO 0 X Z RS485 Receiver Mode INPUTS OUTPUTS RXEN 485/232 B – A R R A B 1 1 < –0.2V 0 Z 1 1 > 0.2V 1 Z 1 1 Inputs Open 1 Z or Shorted to Ground 0 1 X Z Z 6

LTC1387 BLOCK DIAGRAWM RS232 MODE RS485 MODE RS232 MODE RS485 MODE WITHOUT LOOPBACK WITHOUT LOOPBACK WITH LOOPBACK WITH LOOPBACK 1 20 1 20 1 20 1 20 C1 2 19 C2 C1 2 19 C2C1 2 19 C2 C1 2 19 C2 3 18 3 18 3 18 3 18 VDD VCC VDD VCC VDD VCC VDD VCC A 4 17 RA A 45 1167 RA 17 RA 1167 RA 5 16 B RB 16 RB B RB 15 RB 15 6 15 6 DY 6 15 6 DY Y DY Y Y DY Y 7 7 7 14 Z 7 14 Z 14 485/232Z 8 13 ODNZ 485/232* 8 1134 OSLNEW 485/232Z 8 13 DZON 485/232* 8 13 SLOENW DXEN 9 12 RXEN DXEN 9 12 RXEN DXEN* 9 12 RXEN* DXEN* 9 12 RXEN* 10 11 10 11 10 11 10 11 GND VEE GND VEE GND VEE GND VEE *485/232, DXEN, RXEN = VCC LTC1387 • BD TEST CIRCUITS VCC Y R SLEW S1 Y CL A VOD D RL R DR OUT 500W R VOC Z CL B 15pF CL S2 Z 485 = 3V, DXEN = 3V, RXEN = 3V LTC1387 • F02 LTC1387 • F01 LTC1387 • F03 Figure 1. RS485 Driver Figure 2. RS485 Driver/Receiver Figure 3. RS485 Driver Output Test Load Timing Test Circuit Enable/Disable Timing Test Load VCC S1 D Y, Z D Y, Z A, B R RECEIOVUERT 1k CL RL 15pF CL S2 LTC1387 • F05 232 = 0V, DXEN = 3V 232 = 0V, DXEN = 3V, RXEN = 3V LTC1387 • F04 LTC1387 • F06 Figure 4. RS232 Driver Figure 5. RS232 Receiver Figure 6. Receiver Output Timing Test Circuit Timing Test Circuit Enable/Disable Timing Test Load 7

LTC1387 SWITCHIU G WAVEFORW S f = 1MHz: tr £ 10ns: tf £ 10ns (FAST SLEW RATE MODE) f = 100kHz: tr £ 10ns: tf £ 10ns (SLOW SLEW RATE MODE) 3V D 1.5V 1.5V 0V tPLH tPHL VO 90% VDIFF = V(A) – V(B) 90% Z –Y 50% 50% –VO 10% 10% tr 1/2 VO tf Y VO Z tSKEW tSKEW LTC1387 • F07 Figure 7. RS485 Driver Propagation Delays f = 1MHz: tr £ 10ns: tf £ 10ns (FAST SLEW RATE MODE) f = 100kHz: tr £ 10ns: tf £ 10ns (SLOW SLEW RATE MODE) 3V DXEN 1.5V 1.5V 0V tZL tLZ 5V Y, Z 2.3V OUTPUT NORMALLY LOW 0.5V VOL tZH tHZ OUTPUT NORMALLY HIGH VOH 0.5V Z, Y 2.3V 0V LTC1387 • F08 Figure 8. RS485 Driver Enable and Disable Times VOD2 f = 1MHz: tr £ 10ns: tf £ 10ns INPUT B – A 0V 0V –VOD2 tPLH tPHL OUTPUT VOH R 1.5V 1.5V VOL LTC1387 • F09 Figure 9. RS485 Receiver Propagation Delays 3V D 1.5V 1.5V 0V tPHL tPLH VO Y, Z 0V 0V LTC1387 • F10 –VO Figure 10. RS232 Driver Propagation Delays 8

LTC1387 SWITCHIU G WAVEFORW S VIH A, B 1.3V 1.7V VIL tPHL tPLH VOH 2.4V LTC1387 • F11 R 0.8V VOL Figure 11. RS232 Receiver Propagation Delays 3V f = 1MHz: tr £ 10ns: tf £ 10ns RXEN 1.5V 1.5V 0V tZL tLZ 5V R 1.5V OUTPUT NORMALLY LOW 0.5V VOL tZH tHZ OUTPUT NORMALLY HIGH VOH 0.5V R 1.5V 0V LTC1387 • F12 Figure 12. Receiver Enable and Disable Times APPLICATIOUS IUFORWATIOU Basic Theory of Operating Both the interface drivers and the receivers feature three- state outputs. Driver outputs are forced into high The LTC1387 is a single 5V supply, single-port logic impedance when the driver is disabled, in the shutdown reconfigurable RS485/RS232 transceiver with an onboard mode or with the power off. The driver outputs can be charge pump. The interface port offers a flexible combina- forced beyond power supply levels without damage up to tion of an RS485 driver and an RS485 receiver or two – 18V. The receiver inputs can withstand – 25V without RS232 drivers and two RS232 receivers. The RS485 damage. The receiver input resistance is typically 24k in transceiver and the RS232 transceivers are designed to RS485 mode, shutdown mode or power off but drops to share the same I/O pins. A logic input 485/232 controls the 5k in RS232 mode. selection between RS485 and RS232 transceiver modes. The RS485 transceiver supports both RS485 and RS422 In RS485 mode, the DXEN and RXEN control the three- standards, whereas the RS232 transceivers support both state outputs of the driver and receiver respectively. The RS232 and EIA562 standards. With four additional control SLEW input is active during RS485 mode and the logic inputs: ON, DXEN, RXEN and SLEW, the LTC1387 can level controls the differential driver slew rate. This pin has easily be reconfigured via software to adapt to various an internal 5m A pull-up current source during the RS485 communication needs including a one-signal-line RS232 mode. A high logic selects fast differential driver slew rate I/O mode. Four examples of interface port connections are and a low logic selects slow slew rate. In slow slew mode, shown in Figures 13 through 16. the maximum signal bandwidth is reduced, minimizing 9

LTC1387 APPLICATIOUS IUFORWATIOU EMI and signal reflection problems. Slow slew rate sys- All the interface driver outputs are fault protected by a tems can often use improperly terminated or even current limiting and thermal shutdown circuit. The thermal unterminated cables with acceptable results. The RS485 shutdown circuit disables both the RS232 and RS485 differential input receiver features an offset input thresh- driver outputs when the die temperature reaches 150(cid:176) C. old of –80mV at 0V common mode voltage. This allows The thermal shutdown circuit reenables the drivers when the receiver output to have a known High output state the die temperature cools to 135(cid:176) C. when the inputs are open or shorted. The receiver also A loopback mode enables internal connections from driver features an input hysteresis of 40mV. The charge pump outputs to receiver inputs for self-test. The driver outputs can be kept active regardless of the state of DXEN and are not isolated from the external loads during loopback. RXEN pins by keeping the ON pin High. This improves the receiver response time by removing the 100m s charge The charge pump generates boosted positive voltage VDD pump start-up time. and negative voltage VEE for true RS232 levels from a single 5V V supply. The charge pump requires four CC In RS232 mode, the drivers and receivers can be selected 0.1m F capacitors. from the Function Tables with control inputs ON, RXEN and DXEN. The receivers feature a typical 0.6V input hysteresis. LTC1387 RS232 RS485 A RA A RA INTERFACE RS485 B B RB RB Y DY DY DX/RX Z DZ/SLEW VCC DZ ON CONTROLLER RXEN RXEN DXEN DXEN 485/232 MODE RS232 RS232 RS485 RS485 SHUTDOWN TRANSMIT MODE RECEIVE MODE TRANSMIT MODE RECEIVE MODE MODE RXEN = 0 RXEN = 1 RXEN = 0 RXEN = 1 RXEN = 0 DXEN = 1 DXEN = 0 DXEN = 1 DXEN = 0 DXEN = 0 MODE = 0 MODE = 0 MODE = 1 MODE = 1 MODE = X 1387 • F13 Figure 13. Half-Duplex RS232 (1-Channel), Half-Duplex RS485 10

LTC1387 APPLICATIOUS IUFORWATIOU LTC1387 RS232 RS485 A RA A TXD RA INTERFACE RX RS232 RS485 B B RB RXD RB Y DY CONTROLLER DY DX Z DZ/SLEW VCC DZ ON RS232 RS485 RS485 SHUTDOWN MODE TRANSMIT MODE RECEIVE MODE MODE RXEN RXEN RXEN = 1 RXEN = 0 RXEN = 1 RXEN = 0 DXEN DXEN DXEN = 0 DXEN = 1 DXEN = 0 DXEN = 0 485/232 MODE MODE = 0 MODE = 1 MODE = 1 MODE = 0 1387 • F14 Figure 14. Full-Duplex RS232 (1-Channel), Half-Duplex RS485 LTC1387 RS232 RS485 A RA A RXD RA RX RS485 B B RB RB INTERFACE RS232 RS485 Y DY Y CONTROLLER TXD DY DX RS485 Z DZ/SLEW Z VCC RS232 RS485 SHUTDOWN DZ ON MODE MODE MODE RXEN RXEN RXEN = 1 RXEN = 1 RXEN = 0 DXEN DXEN DXEN = 1 DXEN = 1 DXEN = 0 485/232 MODE MODE = 0 MODE = 1 MODE = X 1387 • F15 Figure 15. Full-Duplex RS232 (1-Channel), Full-Duplex RS485/RS422 LTC1387 RS232 RS485 A RA A RXD RA RX1 RS232 RS485 B B RB RX2 CTS RB INTERFACE RS232 RS485 Y DY Y CONTROLLER TXD DY DX1 RS232 RS485 Z DZ/SLEW RS232 RS485 SHUTDOWN Z RTS DZ ON DOXN2/SLEW OMNO =D E1 OMNO =D E1 OMNO =D E0 RXEN RXEN RXEN = 1 RXEN = 1 RXEN = 0 DXEN DXEN DXEN = 1 DXEN = 1 DXEN = 0 485/232 MODE MODE = 0 MODE = 1 MODE = X 1387 • F16 Figure 16. Full-Duplex RS232 (2-Channel), Full-Duplex RS485/RS422 with SLEW Control Information furnished by Linear Technology Corporation is believed to be accurate and reliable. 11 However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

LTC1387 PACKAGE DESCRIPTIOUN Dimensions in inches (millimeters) unless otherwise noted. G Package 20-Lead Plastic SSOP (5.3mm) (Reference LTC DWG # 05-08-1640) 6.90 – 7.50* 5.00 – 5.60** (.272 – .295 ) (.197 – .221) 2.0 20191817161514131211 (.079) 1.25 – 0.12 0° – 8° 7.40 – 8.20 7.8 – 8.2 5.3 – 5.7 0.09 – 0.25 0.55 – 0.95 0.65 (.291 – .323) (.0035 – .010) (.022 – .037) (.0256) BSC 0.05 NOTE: 0.22 – 0.38 (.002) 1. CONTROLLING DIMENSION: MILLIMETERS (.009 – .015) G20 SSOP 0802 MILLIMETERS 2. DIMENSIONS ARE IN (INCHES) 1 2 3 4 5 6 7 8 9 10 0.42 – 0.03 0.65 BSC 3. DRAWING NOT TO SCALE RECOMMENDED SOLDER PAD LAYOUT *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED .152mm (.006") PER SIDE **DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED .254mm (.010") PER SIDE SW Package 20-Lead Plastic Small Outline (Wide 0.300) (LTC DWG # 05-08-1620) 0.496 – 0.512* (12.598 – 13.005) 0.291 – 0.299** 20 19 18 17 16 15 14 13 12 11 (7.391 – 7.595) 0.093 – 0.104 0.037 – 0.045 0.010 – 0.029 · 45(cid:176) (2.362 – 2.642) (0.940 – 1.143) (0.254 – 0.737) 0° – 8° TYP NOTE 1 0.394 – 0.419 (10.007 – 10.643) 0.050 (00..020299 –– 00..031330) NOTE 1(00..041066 –– 01..025700) (1T.2Y7P0)0.014 – 0.019 (00..010042 –– 00..031025) (0.356 – 0.482) NOTE: TYP 1. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS. THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS 1 2 3 4 5 6 7 8 9 10 S20 (WIDE) 0396 *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC485 Low Power RS485 Interface Transceiver Single 5V Supply, Wide Common Mode Range LT®1137A Low Power RS232 Transceiver – 15kV IEC-1000-4-2 ESD Protection, Three Drivers, Five Receivers LTC1320 AppleTalk® Transceiver AppleTalk/LocalTalk® Compliant LTC1321/LTC1322/LTC1335 RS232/EIA562/RS485 Transceivers Configurable LTC1323 Single 5V AppleTalk Transceiver AppleTalk /LocalTalk Compliant 10kV ESD LTC1334 Single Supply RS232/RS485 Transceiver Single 5V Supply, Configurable LTC1347 5V Low Power RS232 Transceiver Three Drivers/Five Receivers, Five Receivers Alive in Shutdown AppleTalk and LocalTalk are registered trademarks of Apple Computer Corp. 12 Linear Technology Corporation sn1387 1387fs LT/GP 0197 7K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 l (408) 432-1900 FAX: (408) 434-0507 l TELEX: 499-3977 l www.linear-tech.com ª LINEAR TECHNOLOGY CORPORATION 1997

Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: A nalog Devices Inc.: LTC1387CG#TRPBF LTC1387ISW#PBF LTC1387CSW#TR LTC1387CSW LTC1387CSW#TRPBF LTC1387ISW#TR LTC1387CG LTC1387IG LTC1387CG#PBF LTC1387IG#TRPBF LTC1387IG#PBF LTC1387ISW#TRPBF LTC1387ISW LTC1387IG#TR LTC1387CG#TR LTC1387CSW#PBF