SN74LS645-1NS Equivalent & Substitute Parts

Part Overview

The SN74LS645-1NS is a non-inverting transceiver logic integrated circuit manufactured by Texas Instruments. This device functions as a 1-element, 8-bit transceiver with 3-state output capability, housed in a 20-SOIC surface mount package. The part is classified as Last Time Buy, indicating limited availability and the necessity to identify equivalent alternatives for ongoing design requirements and inventory planning.

Substiute Parts

SN74LS645-1NS

Texas InstrumentsIn Stock: 1118SN74LS645-1NS Datasheet

Current PartRFQ

SN74LS645-1NSR

Texas InstrumentsIn Stock: 844SN74LS645-1NSR Datasheet

MFR RecommendedRFQ

SN74LS245NS

Texas InstrumentsIn Stock: 1324SN74LS245NS Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the SN74LS645-1NS is determined by strict adherence to the following electrical and mechanical parameters:

Critical Substitution Parameters:

• Logic Type: Transceiver, Non-Inverting
• Number of Elements: 1
• Number of Bits per Element: 8
• Output Type: 3-State
• Voltage - Supply: 4.75V ~ 5.25V
• Operating Temperature: 0°C ~ 70°C (TA)
• Package / Case: 20-SOIC (0.209", 5.30mm Width)
• Mounting Type: Surface Mount

Two substitute parts meet these criteria:

MFR Recommended Substitute: SN74LS645-1NSR (Tape & Reel packaging variant, Active product status)

Parametric Equivalent: SN74LS245NS (Tube packaging variant, Last Time Buy product status)

Both substitutes maintain identical functional specifications, electrical parameters, and physical package dimensions as the main part.

Parameter Comparison

Engineering Selection Recommendations

SN74LS645-1NSR (MFR Recommended Substitute):

This part is the manufacturer-recommended alternative to SN74LS645-1NS. It maintains identical electrical and mechanical specifications with one exception: output low current is rated at 48mA versus 24mA on the original part. The SN74LS645-1NSR carries Active product status, ensuring long-term availability and supply chain continuity. Packaging is supplied in Tape & Reel format, suitable for automated assembly processes. All compliance certifications including ROHS3, REACH Unaffected, and ECCN EAR99 are maintained.

SN74LS245NS (Parametric Equivalent):

This part provides functional equivalence with identical electrical parameters and package dimensions. Output current specifications match the original part (15mA high, 24mA low). The SN74LS245NS is supplied in Tube packaging and carries Last Time Buy status, similar to the original part. This option is suitable for applications where Tape & Reel packaging is not required and where existing inventory management practices accommodate Last Time Buy components.

Selection between these substitutes depends on supply chain requirements, packaging format compatibility with assembly processes, and long-term availability needs.

Frequently Asked Questions (FAQ)

Q: Can SN74LS645-1NSR be used as a direct replacement for SN74LS645-1NS?

A: Yes. Both parts are electrically and mechanically compatible. The SN74LS645-1NSR has higher output low current capability (48mA vs. 24mA), which does not restrict its use in applications designed for the original part. The primary difference is packaging format (Tape & Reel vs. Prototype) and product status (Active vs. Last Time Buy).

Q: What is the difference between SN74LS645-1NSR and SN74LS245NS?

A: Both parts are functionally equivalent transceivers with identical logic type, element count, bit width, and package dimensions. The key difference is output low current: SN74LS645-1NSR provides 48mA while SN74LS245NS provides 24mA. Packaging differs (Tape & Reel vs. Tube). SN74LS645-1NSR has Active status; SN74LS245NS has Last Time Buy status.

Q: Are all three parts pin-compatible?

A: Yes. All three parts use the 20-SOIC package with identical pinout and electrical interface specifications. They are mechanically and electrically interchangeable at the board level.

Q: What does Last Time Buy status mean?

A: Last Time Buy indicates the manufacturer will no longer produce the part after current inventory is depleted. For long-term production requirements, the Active status alternative (SN74LS645-1NSR) is recommended.

Q: Are these parts RoHS compliant?

A: Yes. All three parts are ROHS3 Compliant with Moisture Sensitivity Level 1 (Unlimited), indicating no moisture sensitivity restrictions during storage and handling.

Q: Which substitute should be selected for new designs?

A: Selection is based on supply chain and assembly requirements. SN74LS645-1NSR (Active status, Tape & Reel) is recommended for new designs requiring long-term availability and automated assembly. SN74LS245NS is suitable where Tube packaging is acceptable and Last Time Buy status is not a constraint.

Q: Do these parts require different PCB layouts or assembly processes?

A: No. All three parts use identical 20-SOIC package dimensions (0.209", 5.30mm Width) and surface mount technology. PCB layouts and assembly processes are interchangeable. Only packaging format differs (Prototype, Tape & Reel, or Tube), which affects handling and automated placement compatibility.