SN74LS21NS Equivalent & Substitute Parts

Part Overview

The SN74LS21NS is a dual 4-input AND gate logic integrated circuit manufactured by Texas Instruments. This component belongs to the 74LS logic family and is housed in a 14-pin SOIC surface mount package. The SN74LS21NS is currently in Last Time Buy status, indicating that original inventory is being phased out. Finding equivalent substitute parts is necessary to ensure continued availability for new designs and production requirements.

Substiute Parts

SN74LS21NS

Texas InstrumentsIn Stock: 2172SN74LS21NS Datasheet

Current PartRFQ

SN74LS21NSR

Texas InstrumentsIn Stock: 4055SN74LS21NSR Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the SN74LS21NS is determined by strict equivalence across the following critical parameters:

• Logic Function: Dual 4-input AND gate configuration
• Electrical Specifications: Supply voltage range (4.75V ~ 5.25V), propagation delay (20ns @ 5V, 15pF), and output current ratings (400µA high, 8mA low)
• Package Compatibility: 14-pin SOIC surface mount package with identical physical dimensions
• Compliance Standards: ROHS3 compliance, REACH unaffected status, and EAR99 classification
• Base Product Number: 74LS21 series designation

The SN74LS21NSR qualifies as a direct substitute based on identical electrical performance, package specifications, and compliance certifications. The primary difference is packaging format (Tape & Reel versus Tube) and active product status, which does not affect functional compatibility.

Parameter Comparison

Engineering Selection Recommendations

The SN74LS21NSR is the direct equivalent substitute for the SN74LS21NS. Both parts are manufactured by Texas Instruments and share identical electrical specifications, package dimensions, and compliance certifications. The SN74LS21NSR is recommended for new designs and production orders due to its Active product status, whereas the SN74LS21NS is in Last Time Buy phase.

Selection between these parts should be based on:

• Availability Requirements: The SN74LS21NSR offers continued long-term availability as an active product
• Packaging Logistics: Choose based on procurement volume and supply chain requirements (Tube versus Tape & Reel)
• Compliance Verification: Both parts meet ROHS3 and REACH requirements for regulated markets
• Cost Considerations: Packaging format may influence unit pricing and minimum order quantities

No functional or electrical differences exist between these parts. Direct substitution is possible without circuit redesign or performance impact.

Frequently Asked Questions (FAQ)

Q: Can the SN74LS21NSR be used as a direct replacement for the SN74LS21NS in existing designs?

A: Yes. The SN74LS21NSR is electrically and mechanically identical to the SN74LS21NS. Both parts feature the same dual 4-input AND gate configuration, supply voltage range, propagation delay, output current ratings, and 14-SOIC package dimensions. Direct substitution requires no circuit modifications.

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

A: Tube packaging is used for smaller quantities and manual assembly processes. Tape & Reel (Digi-Reel) packaging is designed for automated pick-and-place assembly equipment and higher-volume production. The electrical and functional specifications are identical; packaging format affects only handling and assembly methodology.

Q: Why is the SN74LS21NS marked as Last Time Buy?

A: Last Time Buy status indicates that Texas Instruments is discontinuing this specific packaging variant. The SN74LS21NSR, which uses Tape & Reel packaging, remains in active production. Customers should transition to the SN74LS21NSR for new designs to ensure long-term supply continuity.

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

A: No. Both the SN74LS21NS and SN74LS21NSR are ROHS3 compliant, REACH unaffected, and classified as EAR99. Moisture sensitivity level is identical at MSL 1 (Unlimited) for both parts.

Q: What are the critical parameters that determine substitution eligibility?

A: Substitution eligibility is determined by matching the logic function (dual 4-input AND gate), electrical specifications (4.75V ~ 5.25V supply, 20ns propagation delay), package type (14-SOIC surface mount), and compliance certifications (ROHS3, REACH). The SN74LS21NSR meets all these criteria.