74HC/HCT4538

The 74HC/HCT4538 are high-speed Si-gate CMOS devices and are pin compatible with "4538" of the "4000B" series. They are specified in compliance with JEDEC standard no. 7A.

The 74HC/HCT4538 are dual retriggerable-resettable monostable multivibrators. Each multivibrator has an active LOW trigger/retrigger input (nA0), an active HIGH trigger/retrigger input (nA1) , an overriding active LOW direct reset input (nRD), an output (nQ) and its complement (nQ), and two pins (nCTC and nRCTC) for connecting the external timing components Ct and Rt. Typical pulse width variation over temperature range is ± 0.2%.

The "4538" may be triggered by either the positive or the negative edges of the input pulse. The duration and accuracy of the output pulse are determined by the external timing components Ct and Rt. The output pulse width (T) is equal to 0.7 ´ Rt ´ Ct. The linear design techniques guarantee precise control of the output pulse width.

A LOW level at nRD terminates the output pulse immediately.
Schmitt-trigger action in the trigger inputs of the 74HC/HCT4538 makes the circuit highly tolerant to slower rise and fall times.