MM74HC4538M

Overview

The MM74HC4538M is a dual retriggerable precision monostable multivibrator implemented in advanced silicon-gate CMOS technology. It features Schmitt trigger inputs for both positive and negative transitions, allowing unlimited rise and fall times on trigger signals. The device operates within a supply voltage range of 2V to 6V and includes a clear input that resets the output when taken low. Pulse width stability is maintained across wide temperature and supply variations using linear CMOS techniques.

Feature Summary

• Retriggerable operation allows pulse extension if triggered repeatedly during timing out
• Schmitt trigger inputs eliminate restrictions on trigger signal rise and fall times
• Outputs directly interface with CMOS, NMOS, and TTL logic families
• Includes a clear input function to force outputs to defined states

Applications

• Pulse generation and timing circuits
• Debouncing switches or contacts
• Frequency division
• Timing delay applications

Procurement Notes

Verify the specific package configuration against the ordering code suffix. Confirm the manufacturer origin, as this part was originally produced by Fairchild Semiconductor before acquisition. Ensure compatibility with existing design constraints regarding power supply ranges and operating temperatures. Check for any lifecycle status updates or obsolescence notices from current distributors.

Selection Notes

Select this component when precise pulse generation with retrigger capability is required. It is suitable for designs needing high noise immunity and low input current typical of CMOS technology. Consider the pinout compatibility with CD4528 and CD4538 devices if migrating from other monostable families. Evaluate the external timing components RX and CX to achieve the desired pulse width according to the specified equation.

Part Context

This device belongs to the HC series of high-speed CMOS logic functions. It provides two independent monostable multivibrators in a single package. The technology offers speeds comparable to low-power Schottky TTL while retaining the low power consumption and high noise immunity characteristics inherent to CMOS circuits. It is designed for general-purpose digital timing applications.

Replacement Considerations

The datasheet confirms pin compatibility with the CD4528 and CD4538 one-shots. These devices may serve as functional substitutes if electrical specifications such as propagation delay and supply voltage ranges are verified to match the application requirements.