74VHC123ASJ

Overview

The Fairchild Semiconductor 74VHC123ASJ is a dual retriggerable monostable multivibrator belonging to the 74VHC (Very High Speed CMOS) logic family. It provides two independent timing circuits within a single package, designed for generating precise pulse widths or delaying signals in digital systems. The device operates on a supply voltage range of 2.0 V to 5.5 V and features Schmitt-trigger inputs on both A and B channels to tolerate slow input rise and fall times. It supports direct reset functionality and is available in a 16-pin SOIC narrow body surface-mount package.

Feature Summary

• Dual independent retriggerable monostable multivibrator circuits
• Schmitt-trigger inputs for noise immunity and slow signal tolerance
• Direct reset capability to terminate output pulses immediately
• CMOS construction ensuring low power consumption

Applications

• Pulse width generation and timing control
• Debouncing mechanical switches
• Frequency division and pulse stretching
• Delay line applications in digital logic systems

Procurement Notes

Verify the specific suffix 'SJ' against official Fairchild/ON Semiconductor documentation to confirm the exact package type and tape/reel specifications. Ensure compatibility with existing PCB footprints and soldering profiles. Confirm RoHS compliance status for current production runs as legacy data may vary.

Selection Notes

Select this component when dual-channel monostable timing is required in space-constrained designs. The VHC series offers speed comparable to LS-TTL with lower power. Verify that the required pulse width range aligns with external resistor-capacitor values and that the supply voltage matches the system rail between 2V and 5.5V.

Part Context

This part belongs to the widely adopted 74VHC123 family, which serves as a high-speed CMOS alternative to older TTL-based monostable multivibrators. The 'A' designation typically indicates an enhanced version of the standard 74VHC123, often featuring improved switching characteristics or updated manufacturing processes while maintaining pin compatibility.

Replacement Considerations

Direct substitutes include the 74VHC123AJ from ON Semiconductor and compatible parts from Texas Instruments such as the SN74VHC123DR. Ensure replacement packages match the original footprint and verify that electrical parameters like propagation delay and output drive current meet design requirements.