Texas Instruments SN54AHC123A

the ahc123a devices are dual retriggerable monostable multivibrators designed for 2-v to 5.5-v vcc operation. these edge-triggered multivibrators feature output pulse-duration control by three methods. in the first method the a\ input is low and the b input goes high. in the second method the b input is high and the a\ input goes low. in the third method the a\ input is low the b input is high and the clear (clr)\ input goes high. the output pulse duration is programmed by selecting external resistance and capacitance values. the external timing capacitor must be connected between cext and rext/cext (positive) and an external resistor connected between rext/cext and vcc. to obtain variable pulse durations connect an external variable resistance between rext/cext and vcc. view all in datasheet