SN74221NE4

Overview

The SN74221NE4 is a dual monostable multivibrator manufactured by Texas Instruments, housed in a 16-pin plastic DIP package. It operates within a supply voltage range of 4.75 V to 5.25 V and supports an operating temperature range of 0°C to 70°C. The device features two independent circuits with negative-transition-triggered (A input) and positive-transition-triggered (B input) inputs. Pulse width is determined by external timing components using the relationship tw(out) ≈ 0.7 CextRext.

Feature Summary

• Features jitter-free operation over more than six decades of timing capacitance and one decade of resistance.
• Includes Schmitt-trigger circuitry on the B input for noise immunity against slow transition rates.
• Provides an overriding clear function to terminate output pulses independently of timing components.
• Maintains pulse-width stability virtually independent of supply voltage and temperature variations.

Applications

• Timing generation and pulse stretching
• Debouncing switches
• Delay line implementation

Procurement Notes

Verify that the ordering suffix NE4 corresponds to the specified PDIP-16 tube packaging and lead finish. Confirm RoHS compliance status and ensure the component meets MIL-PRF-38535 requirements if military-grade reliability is necessary for the application.

Selection Notes

Select this component when pin compatibility with SN54123 or SN74123 devices is required without retrigger functionality. Ensure external timing resistors are selected within the 1.4 kΩ to 40 kΩ range for optimal jitter-free performance at standard logic levels.

Part Context

This device belongs to the SN54/74221 family of dual monostable multivibrators. It offers electrical characteristics virtually identical to the SN54121/SN74121 series but utilizes a different pinout compatible with the SN54123/SN74123 family. It serves as a direct replacement for systems requiring non-retriggerable single-shot behavior.

Replacement Considerations

SN74LS221N

FAQ

How does the SN74221NE4 handle slow input transitions?

The B input incorporates Schmitt-trigger circuitry, allowing jitter-free triggering from inputs with transition rates as slow as 1 V/s.

What is the maximum recommended external timing resistance?

For the SN74221 variant, the maximum recommended external timing resistance is 40 kΩ to maintain jitter-free operation.