SN74ALS21AD Equivalent & Substitute Parts

Part Overview

The SN74ALS21AD is a dual 4-input AND gate logic integrated circuit manufactured by Texas Instruments in 14-SOIC surface mount packaging. This component is classified as Last Time Buy, indicating limited availability from original stock. The SN74ALS21AD performs fundamental AND logic operations across two independent channels, each accepting four input signals. Substitution becomes necessary due to inventory constraints and product lifecycle status, requiring identification of functionally equivalent alternatives that maintain electrical and mechanical compatibility.

Substiute Parts

SN74ALS21AD

Texas InstrumentsIn Stock: 1457SN74ALS21AD Datasheet

Current PartRFQ

SN74ALS21ADR

Texas InstrumentsIn Stock: 3710SN74ALS21ADR Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the SN74ALS21AD is determined by strict equivalence across the following critical parameters:

• Logic function: Dual 4-input AND gate configuration
• Electrical specifications: Supply voltage range 4.5V ~ 5.5V, output current ratings 400µA high and 8mA low, input logic thresholds at 0.8V low and 2V high
• Timing characteristics: Maximum propagation delay of 15ns at 5V with 50pF load
• Operating temperature range: 0°C ~ 70°C
• Package format: 14-SOIC surface mount with 0.154" width (3.90mm)
• Compliance standards: ROHS3 compliance and MSL Level 1

The SN74ALS21ADR qualifies as a direct substitute based on identical electrical performance, timing specifications, and package geometry. The primary distinction is packaging format: the SN74ALS21AD is supplied in Tube packaging, while the SN74ALS21ADR is supplied in Tape & Reel format. Both maintain full functional and electrical equivalence.

Parameter Comparison

Engineering Selection Recommendations

The SN74ALS21ADR is the direct equivalent substitute for the SN74ALS21AD. Both parts are manufactured by Texas Instruments and maintain identical electrical specifications, timing characteristics, and package geometry. The SN74ALS21ADR carries Active product status with higher inventory availability (3600 pcs) compared to the Last Time Buy status of the SN74ALS21AD (1447 pcs).

Selection between these parts should be based on packaging requirements and supply chain considerations. The SN74ALS21AD in Tube packaging is suitable for lower-volume applications or manual assembly processes. The SN74ALS21ADR in Tape & Reel format is optimized for automated assembly and higher-volume production environments. Both parts satisfy ROHS3 compliance and MSL Level 1 requirements, ensuring compatibility with standard manufacturing and storage protocols.

Frequently Asked Questions (FAQ)

Q: Can the SN74ALS21ADR directly replace the SN74ALS21AD in existing designs?

A: Yes. The SN74ALS21ADR is electrically and functionally identical to the SN74ALS21AD. Both parts feature the same 14-SOIC package geometry, supply voltage range, output current ratings, input logic thresholds, and propagation delay specifications. The only difference is the packaging format: Tube versus Tape & Reel.

Q: What is the difference between Tube and Tape & Reel packaging?

A: Tube packaging supplies individual components in a plastic tube, typically used for manual assembly or lower-volume applications. Tape & Reel packaging supplies components on a continuous carrier tape wound on a reel, optimized for automated pick-and-place assembly equipment. Both formats contain the same die and lead configuration.

Q: Are there any compliance or certification differences between these parts?

A: No. Both the SN74ALS21AD and SN74ALS21ADR maintain identical ROHS3 compliance status and Moisture Sensitivity Level 1 rating. They are equivalent for regulatory and environmental requirements.

Q: Why is the SN74ALS21AD marked as Last Time Buy?

A: Last Time Buy status indicates that Texas Instruments has discontinued or is phasing out this product line. The SN74ALS21ADR in Tape & Reel format remains in Active status and represents the current production equivalent. For new designs or long-term supply assurance, the SN74ALS21ADR is the recommended selection.

Q: Can I mix Tube and Tape & Reel packaging in the same production run?

A: Yes, provided your assembly process can accommodate both packaging formats. However, for manufacturing efficiency and consistency, using a single packaging format is standard practice. The SN74ALS21ADR in Tape & Reel format is recommended for automated assembly environments.