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DS75154 Datasheet, PDF (1/8 Pages) National Semiconductor (TI) – Quad Line Receiver
May 1998
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 VCC1 terminal, pin 15, even if power is being
supplied via the alternate VCC2 terminal, pin 16. This pro-
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 kΩ to 7 kΩ 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
Note: When using VCC1 (pin 15), VCC2 (pin 16) may be left open or shorted to VCC1. When using VCC2, VCC1 must be left open or connected to the
threshold control pins.
© 1998 National Semiconductor Corporation DS005795
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