English
Language : 

LT1791_15 Datasheet, PDF (1/18 Pages) Linear Technology – 60V Fault Protected RS485/RS422 Transceivers
Features
n Protected from Overvoltage Line Faults to ±60V
n Pin Compatible with LTC485 and LTC491
n High Input Impedance Supports Up to 128 Nodes
n No Damage or Latchup to ESD
n IEC-1000-4-2 Level 4: ±15kV Air Discharge
n IEC-1000-4-2 Level 2: ±4kV Contact Discharge
n Controlled Slew Rates for EMI Emissions Control
n Guaranteed High Receiver Output State for Floating,
Shorted or Inactive Inputs (LT1785A/LT1791A)
n Outputs Assume a High Impedance When Off or
Powered Down
n Drives Low Cost, Low Impedance Cables
n Short-Circuit Protection on All Outputs
n Thermal Shutdown Protection
n Guaranteed Operation to 125°C
Applications
n Industrial Control Data Networks
n CAN Bus Applications
n HVAC Controls
L, LT, LTC, LTM, µModule, Linear Technology and the Linear logo are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
LT1785/LT1785A/
LT1791/LT1791A
60V Fault Protected
RS485/RS422 Transceivers
Description
The LT®1785/LT1791 are half-duplex and full-duplex differ-
ential 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 out-
putscontrol EMI emissions and improve data transmis-
sion integrity on improperly terminated lines. Drivers are
specified 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.
Typical Application
RO1
RX
RE1
LT1785
DE1
DI1
TX
VCC1
RTERM
GND1
Normal Operation Waveforms at 250kBaud
RO
Y-Z
VCC2
DI
RO2
RX
RE2
LT1785
DE2
RTERM
DI2
TX
GND2
178591 TA01
For more information www.linear.com/LT1785
178591 TA02
178591fd
1