74HC123; 74HCT123
Dual retriggerable monostable multivibrator with reset
Rev. 05 — 13 July 2009
Product data sheet
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 the function table.
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
I
I
I
I
I
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:
N
HBM JESD22-A114E exceeds 2000 V
N
MM JESD22-A115-A exceeds 200 V
I
Specified from
−40 °C
to +85
°C
and from
−40 °C
to +125
°C