SN74HC646NT Equivalent & Substitute Parts

Part Overview

The SN74HC646NT is a Transceiver, Non-Inverting logic IC manufactured by Texas Instruments, featuring 1 element with 8 bits per element and 3-state output capability in a 24-DIP package. This part is classified as Obsolete, making identification of suitable alternatives essential for ongoing design support and procurement continuity. The 24-DIP through-hole package and specific electrical characteristics define the scope for equivalent substitution.

Substiute Parts

SN74HC646NT

Texas InstrumentsIn Stock: 849SN74HC646NT Datasheet

Current PartRFQ

SN74HC646DWR

Texas InstrumentsIn Stock: 3982SN74HC646DWR Datasheet

MFR RecommendedRFQ

74HC86D,653

Nexperia USA Inc.In Stock: 271374HC86D,653 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the SN74HC646NT is evaluated based on the following critical parameters:

Primary Substitution Criteria:

• Logic Type: Transceiver, Non-Inverting
• Number of Elements: 1
• Number of Bits per Element: 8
• Output Type: 3-State
• Voltage Supply Range: 2V ~ 6V
• Current Output Capability: 7.8mA (High and Low)
• Operating Temperature Range: -40°C ~ 85°C minimum
• Series Compatibility: 74HC family

Package Consideration: The original part uses 24-DIP through-hole packaging. Substitutes may employ alternative packaging (such as 24-SOIC surface mount) provided the electrical specifications remain compatible and the functional pinout is preserved.

The substitute list includes one direct functional equivalent (SN74HC646DWR) that maintains identical electrical characteristics while offering an alternative package format and Active product status. The second substitute (74HC86D,653) represents a different logic function (XOR gate) and does not qualify as a true functional equivalent for transceiver applications.

Parameter Comparison

Engineering Selection Recommendations

SN74HC646DWR is the qualified substitute for SN74HC646NT. Both parts share identical electrical specifications, including logic type, element configuration, bit width, output type, current ratings, and voltage supply range. The primary difference is packaging format: SN74HC646DWR uses 24-SOIC surface-mount packaging versus the original 24-DIP through-hole format. SN74HC646DWR carries Active product status, ensuring long-term availability and manufacturing support. Both parts maintain ROHS3 compliance and equivalent reliability ratings.

74HC86D,653 does not qualify as a functional substitute. This part is an XOR (Exclusive OR) gate with 4 channels and 2 inputs per channel, representing a fundamentally different logic function. The 14-SOIC package, reduced output current (5.2mA), and different pin configuration make this part unsuitable for direct replacement in transceiver applications.

For designs currently using SN74HC646NT in through-hole applications, migration to SN74HC646DWR requires PCB redesign to accommodate surface-mount packaging. For new designs or redesigns, SN74HC646DWR is the recommended path forward due to its Active status and continued manufacturer support.

Frequently Asked Questions (FAQ)

Q: Can SN74HC646DWR directly replace SN74HC646NT without circuit modification?

A: Electrical substitution is valid; both parts have identical logic type, element count, bit width, output type, current ratings, and voltage specifications. However, physical substitution requires PCB redesign because SN74HC646DWR uses 24-SOIC surface-mount packaging while SN74HC646NT uses 24-DIP through-hole packaging. Pinout compatibility must be verified against the specific application schematic.

Q: Why is 74HC86D,653 listed as a substitute if it is not functionally equivalent?

A: 74HC86D,653 is listed in the provided substitute data but does not meet the substitution criteria for transceiver applications. This part is an XOR gate and cannot replace the transceiver function of SN74HC646NT. It should not be selected for this application.

Q: What are the key electrical parameters that determine substitution eligibility?

A: Substitution eligibility is determined by: Logic Type (Transceiver, Non-Inverting), Number of Elements (1), Bits per Element (8), Output Type (3-State), Output Current (7.8mA minimum for both High and Low), Supply Voltage Range (2V ~ 6V), and Operating Temperature Range (-40°C ~ 85°C minimum). All these parameters must match or exceed the original specification.

Q: Is the operating temperature range difference between SN74HC646DWR (-40°C ~ 85°C) and 74HC86D,653 (-40°C ~ 125°C) significant for substitution?

A: For SN74HC646NT replacement, the operating temperature range of SN74HC646DWR (-40°C ~ 85°C) is sufficient because it matches the original part specification. The extended range of 74HC86D,653 is irrelevant because this part does not perform the required transceiver function.

Q: What compliance certifications apply to substitute parts?

A: Both SN74HC646DWR and the original SN74HC646NT are ROHS3 Compliant, REACH Unaffected, and carry ECCN EAR99 classification. These certifications ensure regulatory compliance for industrial and commercial applications.