74HC123D,653

The 74HC123D is a dual retriggerable Monostable Multivibrator with a reset. It is pin compatible with low-power Schottky TTL (LSTTL). It comes with an output pulse width control. The Schmitt-trigger action in the nA and nB inputs, makes the circuit highly tolerant to slower input rise and fall times. The output pulse is controlled by three methods, first - the basic pulse is programmed by selection of an external resistor (REXT) and capacitor (CEXT). Second - 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. Third - an internal connection from nRD to the input gates makes it possible to trigger.

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