TEXAS INSTRUMENTS SN74LS122N .

The SN74LS122N is a retriggerable Monostable Multivibrator features output pulse-duration control by three methods. The basic pulse time is programmed by selection of external resistance and capacitance values (see typical application data). It has internal timing resistors that allow the circuits to be used with only an external capacitor, if so desired. Once triggered, the basic pulse duration may be extended by retriggering the gated low-level-active (A) or high-level-active (B) inputs or be reduced by use of the overriding clear. It is provided enough Schmitt hysteresis to ensure jitter-free triggering from the B input with transition rates as slow as 0.1mV/ns.