SN74LS646NT Equivalent & Substitute Parts

Part Overview

The SN74LS646NT is a non-inverting transceiver IC manufactured by Texas Instruments, designed for 8-bit data transmission with 3-state output capability. This component operates within the 74LS logic family and is rated for supply voltages between 4.75V and 5.25V. The part is classified as obsolete, which necessitates identification of functionally equivalent alternatives for ongoing system maintenance and new designs requiring this logic function.

Substiute Parts

SN74LS646NT

Texas InstrumentsIn Stock: 2996SN74LS646NT Datasheet

Current PartRFQ

SN74LS646DW

Texas InstrumentsIn Stock: 1263SN74LS646DW Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the SN74LS646NT is determined by equivalence across the following critical parameters:

• Logic function: Non-inverting transceiver with 1 element, 8 bits per element
• Output configuration: 3-state output capability
• Electrical specifications: 15mA output high current, 24mA output low current
• Supply voltage range: 4.75V ~ 5.25V
• Operating temperature range: 0°C ~ 70°C
• Base product number: 74LS646
• Compliance: ROHS3 compliant, REACH unaffected

The SN74LS646DW maintains functional and electrical equivalence to the SN74LS646NT. The primary difference is packaging format: the substitute uses surface-mount technology (24-SOIC) rather than through-hole mounting (24-DIP).

Parameter Comparison

Engineering Selection Recommendations

The SN74LS646DW is the manufacturer-recommended substitute for the SN74LS646NT. Both components are ROHS3 compliant and REACH unaffected, meeting current environmental and regulatory requirements.

Selection between these parts depends on circuit board design requirements:

• The SN74LS646NT (24-DIP through-hole) is suitable for breadboard prototyping, legacy board retrofitting, and applications where through-hole mounting is specified.
• The SN74LS646DW (24-SOIC surface-mount) is appropriate for modern PCB designs utilizing surface-mount assembly processes and space-constrained layouts.

The SN74LS646DW carries active product status, ensuring continued availability and manufacturing support. The SN74LS646NT is obsolete; new designs should transition to the SN74LS646DW where PCB design permits.

Frequently Asked Questions (FAQ)

Q: Can the SN74LS646DW directly replace the SN74LS646NT in an existing circuit?

A: Electrical and functional equivalence is complete. Direct replacement requires PCB modification to accommodate the different package format: 24-DIP (through-hole) versus 24-SOIC (surface-mount). Pin-to-pin functionality is identical.

Q: What is the primary reason for substitution?

A: The SN74LS646NT is obsolete. The SN74LS646DW provides identical logic function and electrical performance with active manufacturing status.

Q: Are there compliance differences between these parts?

A: Both parts are ROHS3 compliant and REACH unaffected. No compliance advantage exists between the two options.

Q: What are the package dimension differences?

A: The SN74LS646NT uses a 24-DIP package measuring 0.300" (7.62mm) in width. The SN74LS646DW uses a 24-SOIC package measuring 0.295" (7.50mm) in width. Pin pitch and spacing differ between DIP and SOIC formats.

Q: Can both parts operate at identical supply voltages and temperatures?

A: Yes. Both components operate at 4.75V to 5.25V supply voltage and 0°C to 70°C operating temperature range with identical output current specifications (15mA high, 24mA low).