DS75154

Quad Line Receiver

General Description

The DS75154 is a quad monolithic line receiver designed to

satisfy the requirements of the standard interface between

data terminal equipment and data communication equipment

as defined by EIA Standard RS-232C. Other applications are

in relatively short, single-line, point-to-point data transmis-

sion systems and for level translators. Operation is normally

from a single 5V supply; however, a built-in option allows op-

eration from a 12V supply without the use of additional com-

ponents. The output is compatible with most TTL and LS cir-

cuits when either supply voltage is used.

In normal operation, the threshold-control terminals are con-

nected to the V

supplied via the alternate V

vides a wide hysteresis loop which is the difference between

the positive-going and negative-going threshold voltages. In

this mode, if the input voltage goes to zero, the output volt-

age will remain at the low or high level as determined by the

previous input.

For fail-safe operation, the threshold-control terminals are

open. This reduces the hysteresis loop by causing the

negative-going threshold voltage to be above zero. The

positive-going threshold voltage remains above zero as it is

unaffected by the disposition of the threshold terminals. In

the fail-safe mode, if the input voltage goes to zero or an

open-circuit condition, the output will go to the high level re-

gardless of the previous input condition.

Features

n Input resistance, 3 k

Ω to7kΩ over full RS-232C voltage

range

n Input threshold adjustable to meet “fail-safe”

requirements without using external components

n Inverting output compatible with TTL or LS

n Built-in hysteresis for increased noise immunity

n Output with active pull-up for symmetrical switching

speeds

n Standard supply voltage — 5V or 12V

Schematic Diagram

DS005795-1

threshold control pins.

May 1998

© 1998 National Semiconductor Corporation

DS005795

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