MM74HC123AM

Overview

The MM74HC123AM is a dual retriggerable monostable multivibrator utilizing advanced silicon-gate CMOS technology. It features two independent circuits with negative (A) and positive (B) transition triggered inputs, plus a clear input for resetting the output pulse. The device operates within a supply voltage range of 2V to 6V and supports an operating temperature range from -40°C to +85°C. Typical propagation delay is 25 ns, with maximum trigger propagation delays reaching 250 ns at 2.0V. Quiescent supply current is typically 8 µA, rising to 160 µA under standby conditions at 6.0V. Output pulse width is determined by external timing components using the formula PW = REXT × CEXT.

Feature Summary

• Retriggerable operation allows repeated triggering during pulse generation to extend output duration
• Schmitt Trigger inputs on A and B channels accommodate slow rise and fall times up to one second
• Linear CMOS techniques ensure stable pulse width across wide temperature and supply variations
• Outputs can be reset via the Clear input while generating a pulse

Applications

• Pulse generation and timing circuits
• Debouncing switches or contacts
• Frequency division
• Timing delays in digital logic systems

Procurement Notes

Verify component authenticity through authorized distribution channels. Confirm package marking matches M16A designation for 16-Lead SOIC. Check datasheet revisions as Fairchild Semiconductor documentation may reflect legacy manufacturing data prior to acquisition. Ensure external timing components meet specified tolerance requirements for accurate pulse width calculation.

Selection Notes

Select this component when dual independent monostable functions are required in a single package. Verify that the 2V to 6V supply range aligns with system power rails. Consider the 25 ns typical propagation delay for high-speed applications. Ensure external resistor and capacitor values support the desired pulse width without exceeding minimum resistance limits defined in the electrical characteristics.

Part Context

This device belongs to the 74HC series of high-speed CMOS logic integrated circuits. It provides functionality equivalent to low-power Schottky TTL but retains standard CMOS advantages such as low power consumption and high noise immunity. The MM74HC123A is functionally compatible with other 74HC monostable multivibrators, though pin configurations and specific electrical parameters should be verified against individual datasheets before substitution.

Replacement Considerations

Direct substitutes include devices from the same 74HC family with identical pinouts and logical functions. Verify that replacement parts maintain the retriggerable feature and Schmitt trigger inputs if these are critical to the design. Check operating voltage and temperature ranges to ensure compatibility with existing system constraints.