LT1785 - 60V Fault Protected RS485/RS422 Transceivers


  • Protected from Overvoltage Line Faults to ±60V
  • Pin Compatible with LTC485 and LTC491
  • High Input Impedance Supports Up to 128 Nodes
  • No Damage or Latchup to ESD
    IEC-1000-4-2 Level 4: ±15kV Air Discharge
    IEC-1000-4-2 Level 2: ±4kV Contact Discharge
  • Controlled Slew Rates for EMI Emissions Control
  • Guaranteed High Receiver Output State for Floating,
    Shorted or Inactive Inputs
  • Outputs Assume a High Impedance When Off or
    Powered Down
  • Drives Low Cost, Low Impedance Cables
  • Short-Circuit Protection on All Outputs
  • Thermal Shutdown Protection
  • Guaranteed Operation to 125°C

Typical Application

LT1785 Typical Application
LT1785 Typical Application


The LT1785/LT1791 are half-duplex and full-duplex differential bus transceivers for RS485 and RS422 applications which feature on-chip protection from overvoltage faults on the data transmission lines. Receiver input and driver output pins can withstand voltage faults up to ±60V with respect to ground with no damage to the device. Faults may occur while the transceiver is active, shut down or powered off.

Data rates to 250kbaud on networks of up to 128 nodes are supported. Controlled slew rates on the driver outputs control EMI emissions and improve data transmission integrity on improperly terminated lines. Drivers are specifi ed to operate with inexpensive cables as low as 72Ω characteristic impedance.

The LT1785A/LT1791A devices have “fail-safe” receiver inputs to guarantee a receiver output high for shorted, open or inactive data lines. On-chip ESD protection eliminates need for external protection devices.

The LT1785/LT1785A are available in 8-lead DIP and SO packages and the LT1791/LT1791A in 14-lead DIP and SO packages.


CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.

For complete and up to date package information and drawings, please refer to our packaging page

Part Number Package Code Temp Package
LT1785ACN8#PBF N-8 N C 05-08-1510 (N8) Yes
LT1785ACS8#PBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1785ACS8#TRPBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1785AHN8#PBF N-8 N H 05-08-1510 (N8) Yes
LT1785AHS8#PBF SO-8 S8 H 05-08-1610 (S8) Yes
LT1785AHS8#TRPBF SO-8 S8 H 05-08-1610 (S8) Yes
LT1785AIN8#PBF N-8 N I 05-08-1510 (N8) Yes
LT1785AIS8#PBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1785AIS8#TRPBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1785CN8#PBF N-8 N C 05-08-1510 (N8) Yes
LT1785CS8#PBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1785CS8#TRPBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1785HN8#PBF N-8 N H 05-08-1510 (N8) Yes
LT1785HS8#PBF SO-8 S8 H 05-08-1610 (S8) Yes
LT1785HS8#TRPBF SO-8 S8 H 05-08-1610 (S8) Yes
LT1785IN8#PBF N-8 N I 05-08-1510 (N8) Yes
LT1785IS8#PBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1785IS8#TRPBF SO-8 S8 I 05-08-1610 (S8) Yes

LT1785 Package Drawing
LT1785 Package Drawing

Order Info

  • Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
  • Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
  • Please refer to our general ordering information or the product datasheet for more details

Package Variations and Pricing

Part Number Package Temp Price
LT1785ACN8#PBF N-8 C $2.80 $2.35 Yes
LT1785ACS8#PBF SO-8 C $2.85 $2.40 Yes
LT1785ACS8#TRPBF SO-8 C $2.46 Yes
LT1785AHN8#PBF N-8 H $4.24 $2.97 Yes
LT1785AHS8#PBF SO-8 H $4.40 $3.08 Yes
LT1785AHS8#TRPBF SO-8 H $3.14 Yes
LT1785AIN8#PBF N-8 I $3.75 $2.70 Yes
LT1785AIS8#PBF SO-8 I $3.85 $2.80 Yes
LT1785AIS8#TRPBF SO-8 I $2.86 Yes
LT1785CN8#PBF N-8 C $2.30 $1.95 Yes
LT1785CS8#PBF SO-8 C $2.35 $2.00 Yes
LT1785CS8#TRPBF SO-8 C $2.06 Yes
LT1785HN8#PBF N-8 H $3.54 $2.48 Yes
LT1785HS8#PBF SO-8 H $3.61 $2.53 Yes
LT1785HS8#TRPBF SO-8 H $2.59 Yes
LT1785IN8#PBF N-8 I $2.65 $2.25 Yes
LT1785IS8#PBF SO-8 I $2.70 $2.30 Yes
LT1785IS8#TRPBF SO-8 I $2.36 Yes
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* The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Linear Technology sales office or authorized distributor.

Demo Boards

Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Click here to view our complete list of demo boards


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