www.datasheet4u.com
April 2003
LMS75ALS176A
Differential Bus Transceivers
General Description
The LMS75ALS176A is a differential bus/line transceiver
designed for bidirectional data communication on multipoint
bus transmission lines. It is designed for balanced transmis-
sion lines. It meets ANSI Standards TIA/EIA RS422-B, TIA/
EIA RS485-A and ITU recommendation V.11 and X.27. The
LMS75ALS176A combines a TRI-STATE™ differential line
driver and differential input receiver, both of which operate
from a single 5.0V power supply. The driver and receiver
have an active high and active low enable, respectively, that
can be externally connected to function as a direction con-
trol. The driver and receiver differential inputs are internally
connected to form differential input/output (I/O) bus ports
that are designed to offer minimum loading to bus whenever
the driver is disabled or when VCC = 0V. These ports feature
wide positive and negative common mode voltage ranges,
making the device suitable for multipoint applications in
noisy environments. The LMS75ALS176A is available in a
8-Pin SOIC package. It is a drop-in socket replacement to
TI’s SN75ALS176A.
Features
n Bidirectional transceiver
n Meet ANSI standard RS-485-A and RS-422-B
n Low skew, 2ns
n Low supply current, 8mA (max.)
n Wide input and output voltage range
n High output drive capacity ±60mA
n Thermal shutdown protection
n Open circuit fail-safe for receiver
n Receiver input sensitivity ±200mV
n Receiver input hysteresis 10mV (min.)
n Single supply voltage operation, 5V
n Glitch free power-up and power-down operation
n Data rates up to 35 Mbaud
n Pin and functional compatible with TI’s SN75ALS176A
n 8-Pin SOIC
Applications
n Network hubs, bridges, and routers
n Point of sales equipment (ATM, barcode readers,…)
n Industrial programmable logic controllers
n High speed parallel and serial applications
n Multipoint applications with noisy environment
Typical Application
20047801
A Typical multipoint application is shown in the above figure. Terminating resistors, RT, are typically required but only located at the two ends of the cable.
Pull up and pull down resistors maybe required at the end of the bus to provide failsafe biasing. The biasing resistors provide a bias to the cable when all
drivers are in TRI-STATE, See National Application Note, AN-847 for further information.
© 2003 National Semiconductor Corporation DS200478
www.national.com
