General Description

The DM74LS221 is a dual monostable multivibrator with

Schmitt-trigger input. Each device has three inputs permitting

the choice of either leading-edge or trailing-edge triggering.

Pin (A) is an active-LOW trigger transition input and

pin (B) is an active-HIGH transition Schmitt-trigger input

that allows jitter free triggering for inputs with transition

rates as slow as 1 volt/second. This provides the input with

excellent noise immunity. Additionally an internal latching

circuit at the input stage also provides a high immunity to

VCC noise. The clear (CLR) input can terminate the output

pulse at a predetermined time independent of the timing

components. This (CLR) input also serves as a trigger

input when it is pulsed with a low level pulse transition

(

). To obtain the best and trouble free operation from

this device please read operating rules as well as the Fairchild

Semiconductor one-shot application notes carefully

and observe recommendations.

Features

A dual, highly stable one-shot

Compensated for VCC and temperature variations

Pin-out identical to DM74LS123 (Note 1)

Output pulse width range from 30 ns to 70 seconds

Hysteresis provided at (B) input for added noise

immunity

Direct reset terminates output pulse

Triggerable from CLEAR input

DTL, TTL compatible

Input clamp diodes