74AC646SCX Equivalent & Substitute Parts

Part Overview

The 74AC646SCX is a non-inverting transceiver logic IC manufactured by onsemi, featuring 1 element with 8 bits per element and 3-state output capability. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement continuity. The 24-SOP package configuration and 2V to 6V supply voltage range define its operational envelope in digital logic applications requiring bidirectional data transmission with output control.

Key Parameters

Parameter	Value
Manufacturer Part Number	74AC646SCX
Manufacturer	onsemi
Logic Type	Transceiver, Non-Inverting
Number of Elements	1
Number of Bits per Element	8
Output Type	3-State
Current - Output High, Low	24mA, 24mA
Voltage - Supply	2V ~ 6V
Operating Temperature	-40°C ~ 85°C (TA)
Package / Case	24-SOIC (0.295", 7.50mm Width)
Mounting Type	Surface Mount
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution for the 74AC646SCX is determined by the following critical parameters that must remain constant across all equivalent parts:

Logic Type: Transceiver, Non-Inverting
Number of Elements: 1
Number of Bits per Element: 8
Output Type: 3-State
Current - Output High, Low: 24mA, 24mA
Package / Case: 24-SOIC (0.295", 7.50mm Width)
Mounting Type: Surface Mount
Base Product Number: 74AC646 or 74AC652

Substitute parts are grouped into three categories based on their relationship to the main part:

Direct Manufacturer Equivalent (MC74AC646DWG): Identical electrical specifications and packaging from the same manufacturer (onsemi), differing only in packaging format (Tube vs. SOP).

Parametric Equivalents (MC74AC646DWR2G, MC74AC652DWR2G): Maintain all critical electrical and mechanical parameters with identical 24-SOIC packaging. These parts are functionally interchangeable within the same supply voltage and temperature operating ranges.

Similar Parts (CD74AC646M, CD74AC646M96): Texas Instruments equivalents with identical logic function and packaging. These parts operate within an extended supply voltage range (1.5V ~ 5.5V) and wider temperature range (-55°C ~ 125°C), providing enhanced performance margins while maintaining full compatibility with the original 74AC646 base product specifications.

Parameter Comparison

Parameter	74AC646SCX	MC74AC646DWG	MC74AC646DWR2G	MC74AC652DWR2G	CD74AC646M	CD74AC646M96
Manufacturer	onsemi	onsemi	onsemi	onsemi	Texas Instruments	Texas Instruments
Logic Type	Transceiver, Non-Inverting	Transceiver, Non-Inverting	Transceiver, Non-Inverting	Transceiver, Non-Inverting	Transceiver, Non-Inverting	Transceiver, Non-Inverting
Number of Elements	1	1	1	1	1	1
Number of Bits per Element	8	8	8	8	8	8
Output Type	3-State	3-State	3-State	3-State	3-State	3-State
Current - Output High, Low	24mA, 24mA	24mA, 24mA	24mA, 24mA	24mA, 24mA	24mA, 24mA	24mA, 24mA
Voltage - Supply	2V ~ 6V	2V ~ 6V	2V ~ 6V	2V ~ 6V	1.5V ~ 5.5V	1.5V ~ 5.5V
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-55°C ~ 125°C	-55°C ~ 125°C
Package / Case	24-SOIC	24-SOIC	24-SOIC	24-SOIC	24-SOIC	24-SOIC
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Product Status	Obsolete	Obsolete	Obsolete	Obsolete	Last Time Buy	Active
RoHS Status	REACH Unaffected	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

For applications currently using the 74AC646SCX, the following selection criteria apply based on product status and compliance requirements:

Immediate Replacement (Preferred): CD74AC646M96 from Texas Instruments is the recommended primary substitute. This part maintains active product status, ensuring long-term availability and supply chain stability. It provides ROHS3 compliance and operates across an extended supply voltage range (1.5V ~ 5.5V) and temperature range (-55°C ~ 125°C), offering superior performance margins compared to the obsolete original part.

Secondary Alternatives: MC74AC646DWR2G and MC74AC646DWG from onsemi provide direct manufacturer equivalents with identical electrical specifications. These parts are suitable for applications where onsemi sourcing is preferred, though both carry obsolete product status.

Extended Temperature Applications: CD74AC646M provides Last Time Buy status with the same extended operating temperature range (-55°C ~ 125°C) as CD74AC646M96, suitable for designs requiring wider temperature margins.

Packaging Considerations: All substitute parts maintain the 24-SOIC surface mount package, ensuring direct PCB compatibility without layout modifications. Packaging format differences (Tube, Cut Tape, Tape & Reel) do not affect electrical performance and are determined by procurement and assembly requirements.

Frequently Asked Questions (FAQ)

Q: Can MC74AC646DWR2G be used as a direct replacement for 74AC646SCX?

A: Yes. MC74AC646DWR2G maintains identical electrical specifications including logic type, bit configuration, output drive current (24mA), supply voltage range (2V ~ 6V), and operating temperature range (-40°C ~ 85°C). The 24-SOIC package is mechanically and electrically compatible with the original part.

Q: What is the difference between CD74AC646M and CD74AC646M96?

A: Both parts are Texas Instruments equivalents with identical electrical specifications and 24-SOIC packaging. The primary difference is product status: CD74AC646M is Last Time Buy, while CD74AC646M96 is Active. CD74AC646M96 is preferred for new designs due to ongoing availability. The packaging format differs (Tube vs. Tape & Reel) but does not affect electrical performance.

Q: Why do some substitutes have different supply voltage ranges?

A: CD74AC646M and CD74AC646M96 from Texas Instruments specify a supply voltage range of 1.5V ~ 5.5V, compared to the original 2V ~ 6V range. This difference reflects manufacturer specifications but does not prevent substitution in applications operating within the overlapping 2V ~ 5.5V range. For applications requiring operation below 2V or above 5.5V, the original onsemi parts (MC74AC646DWG, MC74AC646DWR2G) must be used.

Q: Are all substitute parts ROHS3 compliant?

A: CD74AC646M, CD74AC646M96, MC74AC646DWG, MC74AC646DWR2G, and MC74AC652DWR2G are all ROHS3 compliant. The original 74AC646SCX carries REACH Unaffected status. All parts are suitable for applications with RoHS compliance requirements.

Q: What is the significance of the 74AC652 base product number in MC74AC652DWR2G?

A: MC74AC652DWR2G uses the 74AC652 base product number but maintains identical electrical specifications and 24-SOIC packaging as the 74AC646 series. This part is functionally equivalent and interchangeable within the specified electrical and mechanical parameters.

Q: Can these parts be used interchangeably in existing designs?

A: Yes, all listed substitute parts are pin-compatible and electrically equivalent within their specified operating ranges. No circuit modifications or PCB layout changes are required. Selection should be based on product status, availability, and compliance requirements for your specific application.

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