Datasheet

1. General description
The 74HC123; 74HCT123 are high-speed Si-gate CMOS devices and are pin compatible
with Low-power Schottky TTL (LSTTL). They are specified in compliance with JEDEC
standard no. 7A.
The 74HC123; 74HCT123 are dual retriggerable monostable multivibrators with output
pulse width control by three methods:
1. The basic pulse is programmed by selection of an external resistor (R
EXT
) and
capacitor (C
EXT
).
2. Once triggered, the basic output pulse width may be extended by retriggering the
gated active LOW-going edge input (nA
) or the active HIGH-going edge input (nB). By
repeating this process, the output pulse period (nQ = HIGH, nQ
= LOW) can be made
as long as desired. Alternatively an output delay can be terminated at any time by a
LOW-going edge on input nRD
, which also inhibits the triggering.
3. An internal connection from nRD
to the input gates makes it possible to trigger the
circuit by a HIGH-going signal at input nRD
as shown in Table 3.
Schmitt-trigger action in the nA
and nB inputs, makes the circuit highly tolerant to slower
input rise and fall times.
The 74HC123; 74HCT123 are identical to the 74HC423; 74HCT423 but can be triggered
via the reset input.
2. Features and benefits
 DC triggered from active HIGH or active LOW inputs
 Retriggerable for very long pulses up to 100 % duty factor
 Direct reset terminates output pulse
 Schmitt-trigger action on all inputs except for the reset input
 ESD protection:
 HBM JESD22-A114F exceeds 2000 V
 MM JESD22-A115-A exceeds 200 V
 Specified from 40 Cto+85C and from 40 Cto+125C
74HC123; 74HCT123
Dual retriggerable monostable multivibrator with reset
Rev. 9 — 19 January 2015 Product data sheet