SN74LV221AD (TEXAS INSTRUMENTS)

The SN74LV221AD is a dual Monostable Multivibrator designed for 2 to 5.5V VCC operation. Each multivibrator has a negative-transition-triggered (A) input and a positive-transition-triggered (B) input, either of which can be used as an inhibit input. This edge-triggered multivibrator features 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 programmable 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 resistor between Rext/Cext and VCC. The output pulse duration also can be reduced by taking CLR low.