1. General description
The 74HC423 is a dual retriggerable monostable multivibrator with output pulse width
control by two methods. The basic pulse time is programmed by selection of an external
resistor (REXT) and capacitor (CEXT). Once triggered, the basic output pulse width may be
extended by retriggering (nA) or (nB). By repeating this process, the output pulse period
(nQ = HIGH, nQ = LOW) can be made as long as desired. When nRD is LOW, it forces
the nQ output LOW, the nQ output HIGH and also inhibits the triggering. Schmitt-trigger
action in the nA and nB inputs, makes the circuit highly tolerant to slower input rise and fall
times. The '423' is identical to the '123' but cannot be triggered via the reset input. Inputs
include clamp diodes. This enables the use of current limiting resistors to interface inputs
to voltages in excess of VCC.
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
 Complies with JEDEC standard no. 7A
 Input levels:
 For 74HC423: CMOS level
 ESD protection:
 HBM JESD22-A114F exceeds 2000 V
 MM JESD22-A115-A exceeds 200 V
 Specified from 40 C to +85 C and from 40 C to +125 C