TLF6386

March 1991

DM74LS123 Dual Retriggerable One-Shot

with Clear and Complementary Outputs

General Description

The DM74LS123 is a dual retriggerable monostable multivi-

brator capable of generating output pulses from a few nano-

seconds to extremely long duration up to 100% duty cycle

Each device has three inputs permitting the choice of either

leading edge or trailing edge triggering Pin (A) is an active-

low transition trigger input and pin (B) is an active-high tran-

sition trigger input The clear (CLR) input terminates the out-

put pulse at a predetermined time independent of the timing

components The clear input also serves as a trigger input

when it is pulsed with a low level pulse transition (

) To

obtain the best trouble free operation from this device

please read the operating rules as well as the NSC one-shot

application notes carefully and observe recommendations

Features

Y

DC triggered from active-high transition or active-low

transition inputs

Y

Retriggerable to 100% duty cycle

Y

Y

Triggerable from CLEAR input

Y

DTL TTL compatible

Y

Input clamp diodes

Functional Description

The basic output pulse width is determined by selection of

the basic pulse width may be extended by retriggering the

gated active-low transition or active-high transition inputs or

be reduced by use of the active-low or CLEAR input Retrig-

gering to 100% duty cycle is possible by application of an

input pulse train whose cycle time is shorter than the output

cycle time such that a continuous ‘‘HIGH’’ logic state is

maintained at the ‘‘Q’’ output

Connection Diagram

Dual-In-Line Package

TLF6386 – 1

Order Number DM74LS123M or DM74LS123N

See NS Package Number M16A or N16E

Function Table

Inputs

Outputs

CLEAR

A

B

Q

Q

LX

X

L

H

XH

X

L

H

XX

L

L

H

HL

u

H

v

H

u

LH

e

A Positive Pulse

e

A Negative Pulse

C1995 National Semiconductor Corporation

RRD-B30M105Printed in U S A