76042012A

Overview

The SN54221 is a dual monostable multivibrator featuring performance characteristics virtually identical to the SN54121. It includes negative-transition-triggered and positive-transition-triggered inputs, with pin assignments identical to the SN54123/SN74123 series. The device provides jitter-free operation over extensive timing ranges using external RC components. Pulse width stability is internally compensated, remaining independent of supply voltage and temperature variations.

Feature Summary

• Features Schmitt-trigger input circuitry for jitter-free triggering from slow transitions
• Includes overriding clear function to terminate output pulses immediately
• Provides high immunity to VCC noise through internal latching circuitry
• Maintains pulse-width stability independent of supply voltage and temperature

Applications

• DC-triggered reset signal generation
• Timing circuits requiring jitter-free operation
• Systems needing direct substitution for SN54123 or SN74LS123 devices

Procurement Notes

Verify the specific ordering suffix against the Package Option Addendum to confirm the exact package type, such as LCCC (FK) or CDIP (J), and the corresponding manufacturer part number like SNJ54LS221FK. Ensure the selected variant matches the required operating temperature range and material specifications before finalizing procurement orders.

Selection Notes

Select this component when replacing SN54123 or SN74LS123 designs without retrigger functionality. Note that capacitor polarity must be reversed compared to those predecessors. Verify that the external timing resistance and capacitance values fall within the recommended jitter-free ranges for the specific device variant chosen.

Part Context

This device belongs to the Texas Instruments ’221 family of dual monostable multivibrators. It serves as a functional equivalent to the older SN54121 series while maintaining physical compatibility with the SN54123/SN74123 pinouts. The family includes standard TTL and LS variants designed for robust pulse generation in digital systems.

Replacement Considerations

SNJ54LS221FK is confirmed as a substitute part number.