HC123A

General Description

The MM54/74HC123A high speed monostable multivibrators (one shots) utilize advanced silicon-gate CMOS technology. They feature speeds comparable to low power Schottky TTL circuitry while retaining the low power and high noise immunity characteristic of CMOS circuits.
Each multivibrator features both a negative, A, and a positive, B, transition triggered input, either of which can be used as an inhibit input. Also included is a clear input that when taken low resets the one shot. The ’HC123 can be triggered on the positive transition of the clear while A is held low and B is held high.
The ’HC123A is retriggerable. That is it may be triggered repeatedly while their outputs are generating a pulse and the pulse will be extended.
Pulse width stability over a wide range of temperature and supply is achieved using linear CMOS techniques. The output pulse equation is simply: PWe(REXT) (CEXT); where PW is in seconds, R is in ohms, and C is in farads. All inputs are protected from damage due to static discharge by diodes to VCC and ground.

Features

■ Typical propagation delay: 25 ns
■ Wide power supply range: 2V–6V
■ Low quiescent current: 80 μA maximum (74HC Series)
■ Low input current: 1 μA maximum
■ Fanout of 10 LS-TTL loads
■ Simple pulse width formula T = RC
■ Wide pulse range: 400 ns to ∞ (typ)
■ Part to part variation: ±5% (typ)
■ Schmitt Trigger A & B inputs enable infinite signal input
rise and fall times.