LMS485E Datasheet, PDF (1/13 Pages) National Semiconductor (TI) – Low Power RS-485 / RS-422 Differential Bus Transceiver

November 2003
LMS485E
Low Power RS-485 / RS-422 Differential Bus Transceiver
General Description
The LMS485E is a low power differential bus/line transceiver
designed for high speed bidirectional data communication 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 LMS485E 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,
respectively, that can be externally connected to function as
a direction control. The driver outputs and receiver 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 common mode
voltage ranges, making the device suitable for multipoint
applications in noisy environments. The LMS485E is avail-
able in 8-Pin SOIC and 8-pin DIP packages. It is a drop-in
replacement to Maxim’s MAX485E.
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 800µA (max)
n Allows up to 32 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 MAX485E
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
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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 DS200866
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