74AC646SC Equivalent & Substitute Parts

Part Overview

The 74AC646SC is a non-inverting transceiver logic integrated circuit manufactured by onsemi, designed for 8-bit bidirectional data transfer with 3-state output capability. This component operates across a 2V to 6V supply voltage range and is housed in a 24-SOP surface mount package. The part is currently classified as obsolete, making identification of functionally equivalent alternatives essential for ongoing system support and component procurement.

Key Parameters

Parameter	Value
Manufacturer Part Number	74AC646SC
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

Substitute parts for the 74AC646SC are identified based on strict electrical and mechanical parameter alignment. The primary substitution criteria are:

Logic type: Transceiver, Non-Inverting
Number of elements: 1
Bits per element: 8
Output type: 3-State
Output current capability: 24mA (high and low)
Package type: 24-SOIC surface mount
Supply voltage compatibility within specified ranges

Two categories of substitutes are identified:

Parametric Equivalent: MC74AC646DWG maintains identical electrical specifications and package dimensions, differing only in packaging format (tube vs. SOP designation).

Similar Parts: CD74AC646M and CD74AC646M96 (Texas Instruments) provide functional equivalence with extended operating temperature range (-55°C to 125°C) and broader supply voltage tolerance (1.5V to 5.5V), though both are classified as similar rather than direct equivalents due to these parameter variations.

Parameter Comparison

Parameter	74AC646SC (Main)	MC74AC646DWG	CD74AC646M	CD74AC646M96
Manufacturer	onsemi	onsemi	Texas Instruments	Texas Instruments
Logic Type	Transceiver, Non-Inverting	Transceiver, Non-Inverting	Transceiver, Non-Inverting	Transceiver, Non-Inverting
Number of Elements	1	1	1	1
Bits per Element	8	8	8	8
Output Type	3-State	3-State	3-State	3-State
Current - Output High, Low	24mA, 24mA	24mA, 24mA	24mA, 24mA	24mA, 24mA
Voltage - Supply	2V ~ 6V	2V ~ 6V	1.5V ~ 5.5V	1.5V ~ 5.5V
Operating Temperature	-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
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Product Status	Obsolete	Obsolete	Last Time Buy	Active
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

MC74AC646DWG is the primary parametric equivalent, offering identical electrical specifications and operating conditions to the 74AC646SC. Both components share onsemi manufacturing and obsolete product status. Selection of MC74AC646DWG is appropriate for direct replacement in applications where the original 2V to 6V supply voltage range and -40°C to 85°C operating temperature are specified.

CD74AC646M96 is recommended for new designs or long-term production requirements. This Texas Instruments component maintains active product status and ROHS3 compliance, providing supply chain continuity. The extended operating temperature range (-55°C to 125°C) and broader supply voltage tolerance (1.5V to 5.5V) offer design flexibility for applications with more demanding environmental specifications. Tape & Reel packaging supports automated assembly processes.

CD74AC646M provides an alternative from Texas Instruments with identical electrical performance to CD74AC646M96, differentiated by Last Time Buy status and tube packaging format. This option is suitable for applications where tube packaging is preferred or where supply chain access to CD74AC646M96 is constrained.

Frequently Asked Questions (FAQ)

Q: Can MC74AC646DWG be used as a direct replacement for 74AC646SC?

A: Yes. MC74AC646DWG is a parametric equivalent with identical logic type, bit configuration, output current capability, supply voltage range, and operating temperature specifications. Both components are housed in 24-SOIC packages with surface mount configuration.

Q: What are the key differences between the onsemi and Texas Instruments alternatives?

A: The primary differences are product status and operating specifications. onsemi parts (74AC646SC and MC74AC646DWG) are obsolete with -40°C to 85°C operating range and 2V to 6V supply voltage. Texas Instruments parts (CD74AC646M and CD74AC646M96) offer extended temperature range (-55°C to 125°C) and broader supply voltage tolerance (1.5V to 5.5V), with CD74AC646M96 maintaining active product status.

Q: Are all substitute parts compatible with the same PCB footprint?

A: Yes. All listed substitutes use the 24-SOIC package with 0.295" width and 7.50mm dimensions, ensuring mechanical and electrical compatibility with existing PCB designs.

Q: Which substitute part should be selected for new production?

A: CD74AC646M96 is the recommended choice for new production due to active product status, ROHS3 compliance, and extended operating specifications. Tape & Reel packaging supports high-volume automated assembly.

Q: What is the significance of the different packaging formats (Tube vs. Tape & Reel)?

A: Tube packaging is suitable for lower-volume applications and manual assembly processes. Tape & Reel packaging is optimized for automated pick-and-place assembly in high-volume production environments. Electrical performance is identical across packaging formats.

Q: Are there supply voltage compatibility concerns when substituting parts?

A: Applications operating within the 2V to 6V range can use any listed substitute without modification. Applications requiring operation below 2V or above 5.5V are limited to the original 74AC646SC or MC74AC646DWG.

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