RS-422 Dual Differential Line Driver and Receiver Pairs

General Description

The DS8922/22A and DS8923A are Dual Differential Line

Driver and Receiver pairs. These devices are designed spe-

cifically for applications meeting the ST506, ST412 and

ESDI Disk Drive Standards. In addition, the devices meet the

requirements of the EIA Standard RS-422.

These devices offer an input sensitivity of 200 mV over a

rated (typically 70 mV) to improve noise margin for slowly

changing input waveforms. An input fail-safe circuit is pro-

vided such that if the receiver inputs are open the output

assumes the logical one state.

The DS8922A and DS8923A drivers are designed to provide

unipolar differential drive to twisted pair or parallel wire trans-

mission lines. Complementary outputs are logically ANDed

and provide an output skew of 0.5 ns (typ.) with propagation

delays of 12 ns.

Both devices feature TRI-STATE outputs. The DS8922/22A

have independent control functions common to a driver and

receiver pair. The DS8923A has separate driver and receiver

control functions.

Power up/down circuitry is featured which will TRI-STATE

the outputs and prevent erroneous glitches on the transmis-

sion lines during system power up or power down operation.

The DS8922/22A and DS8923A are designed to be compat-

ible with TTL and CMOS.

Features

n

12 ns typical propagation delay

n

n

Meets the requirements of EIA Standard RS-422

n

Complementary Driver Outputs

n

High differential or common-mode input voltage ranges

0.2V receiver sensitivity over the input voltage range

n

Receiver input fail-safe circuitry

n

Receiver input hysteresis — 70 mV typical

n

Glitch free power up/down

n

TRI-STATE outputs

Connection Diagrams

DS8922A Dual-In-Line

00851101

Order Number DS8922M, DS8922N,

DS8922AM or DS8922AN

See NS Package Number M16A or N16E

July 2004

© 2004 National Semiconductor Corporation

DS008511

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