SN74LS221NE4

Overview

The SN74LS221NE4 is a dual non-retriggerable monostable multivibrator manufactured by Texas Instruments. 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, each with positive- and negative-transition-triggered inputs. It utilizes external timing components (Rext and Cext) to define output pulse width, which can be varied from 35 ns up to 70 µs. The package type is PDIP-14.

Feature Summary

• Features jitter-free operation over more than six decades of timing capacitance and one decade of resistance.
• Includes Schmitt-trigger input circuitry on the B input for noise immunity.
• Provides overriding clear functionality to terminate output pulses immediately.

Applications

• Timing generation
• Pulse shaping
• Delay lines

Procurement Notes

Verify that the ordering suffix NE4 corresponds to the specific lead-free and RoHS-compliant packaging configuration required for your assembly process. Confirm the manufacturer source, as this part may be distributed by Rochester Electronics or Texas Instruments depending on availability. Ensure the component matches the exact PDIP-14 through-hole specification.

Selection Notes

Select this component when a dual monostable multivibrator with TTL-compatible outputs is required. It serves as a direct pinout-compatible replacement for the SN54123/SN74123 series, provided the capacitor polarity is adjusted. Consider the LS logic family characteristics regarding power consumption and drive capability compared to standard 74-series devices.

Part Context

This device belongs to the SN54/74221 family of dual non-retriggerable monostable multivibrators. It shares identical pin assignments with the SN54123 and SN74123 families, facilitating system upgrades or redesigns without altering the printed circuit board layout. The 'LS' designation indicates Low-power Schottky logic technology.

Replacement Considerations

SN74LS221N

FAQ

How does the SN74LS221NE4 differ from the SN74123 in terms of retriggerability?

The SN74LS221NE4 is a non-retriggerable monostable multivibrator, whereas the SN74123 is retriggerable. They share the same pinout but have different internal triggering behaviors.

What is the maximum recommended external timing resistance for the SN74LS221NE4?

The maximum recommended external timing resistance (Rext) for the SN74LS221NE4 is 100 kΩ.