LMS1487E Datasheet, PDF (1/13 Pages) National Semiconductor (TI) – Low Power RS-485 / RS-422 Differential Bus Transceiver

November 2003
LMS1487E
Low Power RS-485 / RS-422 Differential Bus Transceiver
General Description
The LMS1487E is a low power differential bus/line trans-
ceiver designed for high speed bidirectional data communi-
cation on multipoint bus transmission lines. It is designed for
balanced transmission lines. It meets ANSI Standards TIA/
EIA RS422-B, TIA/EIA RS485-A and ITU recommendation
and V.11 and X.27. The driver outputs and receiver inputs
have ±15kV ESD protection. The LMS1487E combines a
TRI-STATE™ differential line driver and differential input re-
ceiver, both of which operate from a single 5.0V power
supply. The driver and receiver have an active high and
active low, respectively, that can be externally connected to
function as a direction control. The driver outputs and re-
ceiver inputs are internally connected to form a differential
input/output (I/O) bus port that is designed to offer minimum
loading to bus whenever the driver is disabled or when V_CC
= 0V. These ports feature wide positive and negative com-
mon mode voltage ranges, making the device suitable for
multipoint applications in noisy environments. The
LMS1487E is available in 8-Pin SOIC and 8-pin DIP pack-
ages. It is a drop-in replacement to Maxim’s MAX1487E.
Features
n Meet ANSI standard RS-485 and RS-422
n Data rate 2.5 Mbps
n Single supply voltage operation, 5V
n Wide input and output voltage range
n Thermal shutdown protection
n Short circuit protection
n Low quiescent current 660µA (max)
n Allows up to 128 transceivers on the bus
n Open circuit fail-safe for receiver
n Extended operating temperature range −40˚C to 85˚C
n Drop-in replacement to MAX1487E
n Available in 8-pin SOIC and 8-pin DIP packages
Applications
n Low power RS-485 systems
n Network hubs, bridges, and routers
n Point of sales equipment (ATM, barcode scanners,…)
n Local area networks (LAN)
n Integrated service digital network (ISDN)
n Industrial programmable logic controllers
n High speed parallel and serial applications
n Multipoint applications with noisy environment
Typical Application
20085601
A typical multipoint application is shown in the above figure. Terminating resistor, 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 fail-safe 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 DS200856
www.national.com