LINEAR TECHNOLOGY LT1785 LT1785A LT1791 LT1791A Data Sheet User Manual
Summary
The LT1785/LT1791 series are robust differential bus transceivers designed for high-reliability RS485/RS422 applications. Featuring advanced on-chip protection against overvoltage, line faults (up to –60V), and ESD damage, these transceivers ensure data integrity in harsh industrial environments. The manual details the performance specifications, fail-safe protocols, controlled slew rates for EMI control, and robust operation across up to 128 nodes. Ideal for building reliable Industrial Control Data Networks, HVAC controls, and CAN Bus systems requiring superior communications reliability.
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LT1785/LT1785A LT1791/LT1791A 60V Fault Protected
RS485/RS422 Transceivers
FEATURES DESCRIPTIO Protected from Overvoltage Line Faults to ±60V The LT®1785/LT1791 are half-duplex and full-duplex dif- Pin Compatible with LTC485 and LTC491 ferential bus transceivers for RS485 and RS422 applica- High Input Impedance Supports Up to 128 Nodes tions which feature on-chip protection from overvoltage No Damage or Latchup to ESD faults on the data transmission lines. Receiver input and IEC-1000-4-2 Level 4: ±15k V Air Discharge driver output pins can withstand voltage faults up to ±60V IEC-1000-4-2 Level 2: ±4k V Contact Discharge with respect to ground with no damage to the device. Controlled Slew Rates for EMI Emissions Control Faults may occur while the transceiver is active, shut down Guaranteed High Receiver Output State for Floating, or powered off. Shorted or Inactive Inputs
Data rates to 250kbaud on networks of up to 128 nodes are
Outputs Assume a High Impedance When Off or
supported. Controlled slew rates on the driver outputs
Powered Down
control EMI emissions and improve data transmission
Drives Low Cost, Low Impedance Cables
integrity on improperly terminated lines. Drivers are speci-
Short-Circuit Protection on All Outputs
fied to operate with inexpensive cables as low as 72Ω
Thermal Shutdown Protection
characteristic impedance.
APPLICATIO S The LT1785A/LT1791A devices have “fail-safe” receiver
inputs to guarantee a receiver output high for shorted,
Industrial Control Data Networks
open or inactive data lines. On-chip ESD protection elimi-
CAN Bus Applications
nates need for external protection devices.
HVAC Controls
The LT1785/LT1785A are available in 8-lead DIP and SO packages and the LT1791/LT1791A in 14-lead DIP and SO packages. , LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
Normal Operation Waveforms at 250k Baud
RO1 RX
LT1785 RTERM
DI1 TX
RO2 RX
RE2 DI
LT1785 RTERM
DI2 TX 1785/91 TA02
1785/91 TA01
Page Summary Contents For LINEAR TECHNOLOGY LT1785 LT1785A LT1791 LT1791A Data Sheet User Manual
Manual Details
| Brand | Linear |
|---|---|
| Pages | 12 |
| File Size | 203.09 KB |
| Published | June 17, 2026 |
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Frequently Asked Questions
What electrical faults are these transceivers protected from?
They offer protection from overvoltage line faults up to -60V, include on-chip ESD protection, and can withstand IEC-1000-4-2 Level 4 air discharge.
Do I need extra components for fault protection when using these ICs?
No. The built-in features, such as on-chip ESD protection, eliminate the need for external protection devices in many scenarios.
What is the maximum number of nodes supported on a network?
The transceivers support data rates up to 250kbaud on networks consisting of up to 128 nodes.
In what types of electrical or industrial systems can I use this transceiver?
They are suitable for RS485/RS422 applications, industrial control data networks, HVAC controls, and CAN Bus applications.