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LT1785AIS8#TRPBF

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Analog Devices RS-485 / RS-422 ICs, SOIC-8. Pinout cross-checked by two models against the datasheet, KiCad symbol/footprint/3D.

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Contents

README

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LT1785AIS8#TRPBF

Analog Devices · RS-485 / RS-422 ICs · SOIC-8

LT1785AIS8#TRPBF from Analog Devices, in a SOIC-8. Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model); symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin Name Type Function
1 RO output Receiver output is TTL level: high when A ≥ B by 200mV and low when A ≤ B by 200mV, and it goes high impedance when RE is high or the part is powered off.
2 RE input Receiver output enable is a TTL input where logic low enables RO and logic high places RO in high impedance; with RE and DE both disabled the part enters shutdown after a 3µs delay.
3 DE input Driver output enable is a TTL input where logic high enables the driver outputs A and B and logic low places them in high impedance.
4 DI input Driver input is a TTL logic input where logic high drives A high and B low and logic low gives complementary outputs; it should be tied low in CAN bus applications.
5 GND power_in Ground reference pin for the device.
6 A bidirectional Receiver input A forces a high RO when V(A) ≥ V(B) + 200mV and is protected against voltage faults between ±60V; on the LT1785 it is also the driver output A, which is high impedance when DE is low.
7 B bidirectional Receiver input B is protected against voltage faults between ±60V and, when V(A) ≤ V(B) − 200mV, forces RO low; on the LT1785 it is also the driver output B, which is high impedance when DE is low.
8 VCC power_in Positive supply input, specified at 4.75V ≤ VCC ≤ 5.25V for RS422 or RS485 operation, with a 0.1µF low ESR decoupling capacitor placed directly at this pin.

Key specifications

Parameter Value
Manufacturer Analog Devices
Package SOIC-8
Category Interface
Pins 8

Electrical characteristics

Limits as printed in the datasheet (page.json metadata.characteristics carries them as data).

Parameter Symbol Min Typ Max Unit Conditions Page
Differential Driver Output Voltage (Unloaded) VOD1 4.1 5 V IO = 0 4
Differential Driver Output Voltage (With Load), RS422 VOD2 2 2.7 V R = 50Ω (RS422), Figure 1 4
Differential Driver Output Voltage (With Load), RS485 VOD2 1.5 2.45 V R = 27Ω (RS485), Figure 1 4
Differential Driver Output Voltage (With Load), R = 18Ω VOD2 1.2 2.2 V R = 18Ω 4
Change in Magnitude of Driver Differential Output Voltage for Complementary Output States VOD 0.2 V R = 27Ω or R = 50Ω, Figure 1 4
Driver Common Mode Output Voltage VOC 2 2.5 3 V R = 27Ω or R = 50Ω, Figure 1 4
Change in Magnitude of Driver Common Mode Output Voltage for Complementary Output States ∆/VOC/ 0.2 V R = 27Ω or R = 50Ω, Figure 1 4
Input High Voltage VIH 2 V DI, DE, RE 4
Input Low Voltage VIL 0.8 V DI, DE, RE 4
Input Current IIN1 5 µA DI, DE, RE 4
Input Current (A, B) IIN2 -0.15 0.15 mA (LT1791 or LT1785 with DE = 0V) VIN = 12V 4
Input Current (A, B) IIN2 -6 -0.08 mA (LT1791 or LT1785 with DE = 0V) VIN = -7V 4
Input Current (A, B) IIN2 0.3 6 mA (LT1791 or LT1785 with DE = 0V) -60V ≤ VIN ≤ 60V 4
Differential Input Threshold Voltage for Receiver (LT1785A) VTH -0.2 0 V LT1785A/LT1791A: -7V ≤ VCM ≤ 12V 4
Receiver Output High Voltage VOH 3.5 4 V IO = -400µA, VID = 200mV 4
Receiver Output Low Voltage VOL 0.3 0.5 V IO = 1.6mA, VID = -200mV 4
Three-State (High Impedance) Output Current at Receiver -1 1 µA 0V < VOUT < 6V; RE > 2V or Power Off 4
Receiver Input Resistance (LT1785) RIN 50 90 kΩ LT1785 -7V ≤ VCM ≤ 12V 4
Driver Short-Circuit Current, VOUT = HIGH ISC 35 250 mA VOUT = HIGH, Force VO = -7V 4
Driver Short-Circuit Current, VOUT = LOW ISC 35 250 mA VOUT = LOW, Force VO = 12V 4
Driver Output Fault Current -6 6 mA VO = 60V / VO = -60V 4
Receiver Short-Circuit Current -35 35 mA 0V ≤ VO ≤ VCC 4
Driver Three-State Output Current -0.2 0.3 mA -7V ≤ VO ≤ 12V 4
Driver Three-State Output Current -6 6 mA -60V ≤ VO ≤ 60V 4
Supply Current ICC 5.5 9 mA No Load, RE = 0V, DE = 5V 4
Supply Current ICC 4.5 8 mA No Load, RE = 0V, DE = 0V 4
Supply Current ICC 0.2 0.3 mA No Load, RE = 5V, DE = 0V 4
Driver Input to Output (tPLH) tPLH 700 2000 ns Figures 3, 5 5
Driver Input to Output (tPHL) tPHL 700 2000 ns Figures 3, 5 5
Driver Output to Output Skew tSKEW 100 ns Figures 3, 5 5
Driver Rise or Fall Time tr, tf 200 800 2000 ns Figures 3, 5 5
Driver Enable to Output High tZH 500 3000 ns Figures 4, 6 5
Driver Enable to Output Low tZL 800 3000 ns Figures 4, 6 5
Driver Disable Time from Low tLZ 200 5000 ns Figures 4, 6 5
Driver Disable Time from High tHZ 800 5000 ns Figures 4, 6 5
Receiver Input to Output (tPLH) tPLH 400 900 ns Figures 3, 7 5
Receiver Input to Output (tPHL) tPHL 400 900 ns Figures 3, 7 5
Differential Receiver Skew tSKD 200 ns 5
Receiver Enable to Output Low tZL 300 1000 ns Figures 2, 8 5
Receiver Enable to Output High tZH 300 1000 ns Figures 2, 8 5
Receiver Disable from Low tLZ 400 1000 ns Figures 2, 8 5
Receiver Disable from High tHZ 400 1000 ns Figures 2, 8 5
Maximum Data Rate fMAX 250 kbps 5
Time to Shut Down tSHDN 3 µs Figures 2, 6, 8 5
Driver Enable from Shutdown to Output High tZH(SHDN) 12 µs Figures 2, 6; RE = 5V 5
Driver Enable from Shutdown to Output Low tZL(SHDN) 12 µs Figures 2, 6; RE = 5V 5
Receiver Enable from Shutdown to Output High tZH(SHDN) 4 µs Figures 2, 8; DE = 0V 5
Receiver Enable from Shutdown to Output Low tZL(SHDN) 4 µs Figures 2, 8; DE = 0V 5
Supply Voltage VCC 18 V 2
Receiver Enable Input Voltage -0.3 6 V 2
Driver Enable Input Voltage -0.3 6 V 2
Driver Input Voltage -0.3 18 V 2
Receiver Input Voltage -60 60 V 2
Driver Output Voltage -60 60 V 2
Receiver Output Voltage -0.3 V Maximum is (VCC + 6V) 2
Operating Temperature Range (LT1785AI) -40 85 °C 2
Storage Temperature Range -65 150 °C 2
Thermal Resistance, Junction to Ambient (S8) θJA 150 °C/W S8 package; TJMAX = 150°C 2
Supply Voltage for RS422 or RS485 Operation VCC 4.75 5.25 V RS422 or RS485 operation 7

CAD (KiCad official)

  • Symbol: LT1785AIS8#TRPBF
  • Footprint: Package_SO:SOIC-8_3.9x4.9mm_P1.27mm
  • 3D model: SOIC-8 (KiCad packages3D, STEP)
  • 3D model files: lt1785ais8-trpbf-etched.step / lt1785ais8-trpbf-etched.glb carry the MPN laser-etched on the die in a toggleable Adom.LaserEtch group (Fusion-ready); lt1785ais8-trpbf.step / lt1785ais8-trpbf.glb are the bare package body.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

  • Datasheet: Analog Devices datasheet (18 pp, sha256 fdbe7d7ca92ed386, retrieved 2026-10-18, tier: lcsc)
  • Extractor: parts-factory 2.0.0 / extract_pins 0.3, primary claude-haiku-5-5 (text), consensus claude-sonnet-5-5 (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
  • CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF