CD74HC646M Equivalent & Substitute Parts

Part Overview

The CD74HC646M is a transceiver IC with non-inverting logic, designed for 8-bit data transmission with 3-state output capability. Manufactured by Texas Instruments in a 24-SOIC surface mount package, this component operates across a 2V to 6V supply voltage range and supports bidirectional data flow in digital logic applications.

The CD74HC646M is classified as obsolete. Locating equivalent or substitute components is necessary to support legacy system maintenance, design updates, or when original inventory becomes unavailable. Substitute parts must maintain functional compatibility while meeting the electrical and mechanical requirements of the original application.

Substiute Parts

CD74HC646M

Texas InstrumentsIn Stock: 944CD74HC646M Datasheet

Current PartRFQ

74HC86D,653

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

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the CD74HC646M must satisfy the following criteria based on provided electrical and mechanical parameters:

Voltage Compatibility: Supply voltage range must overlap or encompass the 2V to 6V specification of the original part.

Output Characteristics: Output type and current drive capability must support the 3-state output requirement and 7.8mA output current specification.

Logic Family: Parts must belong to the 74HC logic family to ensure timing, noise immunity, and electrical compatibility.

Package Compatibility: Surface mount packaging with compatible pin counts and footprints suitable for 24-SOIC or equivalent land patterns.

Compliance Requirements: RoHS3 compliance and REACH unaffected status must be maintained.

Operating Temperature Range: The substitute must support the -55°C to 125°C operating temperature range or a compatible subset.

Parameter Comparison

Engineering Selection Recommendations

The 74HC86D,653 from Nexperia USA Inc. maintains 74HC logic family compatibility and meets the 2V to 6V supply voltage requirement. Both parts are ROHS3 compliant and carry EAR99 ECCN classification.

The substitute part is currently in active production status, ensuring availability for ongoing applications. The operating temperature range of -40°C to 125°C covers the upper portion of the original specification; applications requiring the full -55°C lower temperature limit must evaluate whether the -40°C minimum is acceptable for the intended use case.

Output current drive capability differs between the parts: the substitute provides 5.2mA versus the original 7.8mA. Circuit designs must confirm that the reduced output current remains sufficient for downstream logic loading.

Package footprint differences exist: the original uses 24-SOIC while the substitute uses 14-SOIC. PCB layout modifications are required to accommodate the different pin count and physical dimensions.

Frequently Asked Questions (FAQ)

Q: Can the 74HC86D,653 directly replace the CD74HC646M without circuit modifications?

A: Direct pin-for-pin replacement is not possible due to different package types (24-SOIC versus 14-SOIC) and pin counts. PCB layout redesign is required. Additionally, the reduced output current specification (5.2mA versus 7.8mA) must be evaluated against circuit loading requirements.

Q: What is the significance of the operating temperature range difference?

A: The CD74HC646M operates from -55°C to 125°C, while the 74HC86D,653 operates from -40°C to 125°C. Applications requiring operation below -40°C cannot use the substitute without alternative component selection. Applications within the -40°C to 125°C range are compatible.

Q: Are both parts compliant with current environmental regulations?

A: Yes. Both the CD74HC646M and 74HC86D,653 are ROHS3 compliant and REACH unaffected, meeting current environmental and regulatory requirements for electronic component use.

Q: What does the obsolete status of the CD74HC646M mean for new designs?

A: Obsolete status indicates the part is no longer manufactured by Texas Instruments. New designs should not incorporate this component. Existing systems using the CD74HC646M should evaluate active alternatives such as the 74HC86D,653 for maintenance and upgrade purposes.

Q: How do supply voltage specifications compare between these parts?

A: Both parts operate within the identical 2V to 6V supply voltage range, ensuring electrical compatibility in this parameter across standard logic supply levels.