74AHC123

The 74AHC123 is a high-speed silicon-gate CMOS device. It is a dual retriggerable monostable multivibrator.

The device has three ways of output pulse-duration control. First, when nA input sets low, the nB input goes high. Second, when nB input sets high, the nA input goes low. Third, when nA input sets low and nB input sets high, the nRD input goes high. Figure 3 shows the output pulse control using retrigger pulse and Figure 4 illustrates the output pulse control using reset input nRD.

The output pulse-duration can be set through the selection of external resistance (RPROG) and capacitance (CPROG) values. All the inputs have Schmitt-trigger actions with sufficient hysteresis to handle slow input rise and fall times.

When started, the gated active low-going edge (nA) input or the active high-going edge (nB) input can help to prolong the basic output pulse-duration. Through it, an ideal output pulse period (nQ = high, nQ = low) can be achieved. Pulse duration can be reduced by a low-going edge on nRD input.