74AC161SC Binary Counter 4-Bit Logic IC Equivalent & Substitute Parts

Part Overview

The 74AC161SC is a 4-bit binary counter logic IC manufactured by onsemi, housed in a 16-SOIC surface mount package. This component functions as a synchronous binary counter with asynchronous reset, capable of counting on positive clock edges at a maximum rate of 167 MHz. The part is currently listed as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Key Parameters

Parameter	Value
Manufacturer Part Number	74AC161SC
Manufacturer	onsemi
Logic Type	Binary Counter
Number of Bits	4
Count Direction	Up
Reset Type	Asynchronous
Timing	Synchronous
Count Rate	167 MHz
Trigger Type	Positive Edge
Supply Voltage Range	2 V ~ 6 V
Operating Temperature	-40°C ~ 85°C
Package / Case	16-SOIC (0.154", 3.90mm Width)
Mounting Type	Surface Mount
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution for the 74AC161SC is determined by strict equivalence across the following critical parameters:

Logic Type: Binary Counter (4-bit, up-counting)
Reset Configuration: Asynchronous reset capability
Timing Architecture: Synchronous operation
Trigger Mechanism: Positive edge triggered
Package Form Factor: 16-SOIC surface mount
Electrical Specifications: Supply voltage range and operating temperature compatibility
Pin Configuration: Identical pinout within the 74AC series

The substitute parts are grouped into two categories based on their relationship to the main part:

Direct Manufacturer Equivalents maintain identical electrical specifications and are sourced from the same manufacturer (onsemi), differing only in packaging format or product status.

Parametric Equivalents from alternative manufacturers (Texas Instruments) provide functional equivalence with minor variations in maximum count rate and operating temperature range, while maintaining the same package footprint and core logic functionality.

Parameter Comparison

Parameter	74AC161SC (onsemi)	MC74AC161DR2G (onsemi)	MC74AC161DG (onsemi)	CD74AC161M (Texas Instruments)
Logic Type	Binary Counter	Binary Counter	Binary Counter	Binary Counter
Number of Bits	4	4	4	4
Count Direction	Up	Up	Up	Up
Reset Type	Asynchronous	Asynchronous	Asynchronous	Asynchronous
Timing	Synchronous	Synchronous	Synchronous	Synchronous
Trigger Type	Positive Edge	Positive Edge	Positive Edge	Positive Edge
Count Rate (Max)	167 MHz	167 MHz	167 MHz	90 MHz
Supply Voltage Range	2 V ~ 6 V	2 V ~ 6 V	2 V ~ 6 V	1.5 V ~ 5.5 V
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-55°C ~ 125°C
Package / Case	16-SOIC	16-SOIC	16-SOIC	16-SOIC
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Product Status	Obsolete	Last Time Buy	Last Time Buy	Discontinued at DiGi Electronics
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

MC74AC161DR2G (onsemi) is the primary direct substitute. This part maintains identical electrical performance to the 74AC161SC while offering improved product status (Last Time Buy vs. Obsolete) and ROHS3 compliance certification. The packaging format (Cut Tape & Digi-Reel) supports automated assembly processes. Current inventory availability is significantly higher (10,035 units).

MC74AC161DG (onsemi) serves as a secondary direct substitute with equivalent electrical specifications and ROHS3 compliance. This variant is supplied in Tube packaging, suitable for manual assembly or lower-volume production runs. Inventory availability is adequate (2,224 units).

CD74AC161M (Texas Instruments) is a parametric equivalent suitable for applications where the reduced maximum count rate (90 MHz vs. 167 MHz) and extended operating temperature range (-55°C ~ 125°C) align with system requirements. This part offers broader temperature coverage and ROHS3 compliance. Selection of this alternative requires confirmation that the 90 MHz count rate specification meets circuit timing requirements.

For new designs or procurement of the obsolete 74AC161SC, MC74AC161DR2G is the recommended first choice based on direct equivalence, compliance status, and inventory availability.

Frequently Asked Questions (FAQ)

Q: Can MC74AC161DR2G directly replace 74AC161SC without circuit modification?

A: Yes. Both parts share identical electrical specifications, pinout, and package footprint (16-SOIC). No circuit modifications are required for direct substitution.

Q: What is the difference between MC74AC161DR2G and MC74AC161DG?

A: Both parts are electrically identical. The difference is packaging format: MC74AC161DR2G is supplied in Cut Tape & Digi-Reel format for automated assembly, while MC74AC161DG is supplied in Tube format for manual assembly or lower-volume applications.

Q: Is CD74AC161M a suitable replacement for 74AC161SC?

A: CD74AC161M is functionally equivalent but with two parameter differences: maximum count rate is 90 MHz (vs. 167 MHz) and operating temperature range is -55°C ~ 125°C (vs. -40°C ~ 85°C). Substitution is valid only if the application's clock frequency does not exceed 90 MHz and the extended temperature range does not introduce incompatibilities with other circuit components.

Q: Are all substitute parts ROHS3 compliant?

A: MC74AC161DR2G and MC74AC161DG are both ROHS3 compliant. CD74AC161M is also ROHS3 compliant. The original 74AC161SC does not specify RoHS status.

Q: What is the significance of "Last Time Buy" status for MC74AC161DR2G and MC74AC161DG?

A: Last Time Buy status indicates these parts are in the final phase of availability from the manufacturer. While currently in stock, future procurement may become limited. For long-term production requirements, secure adequate inventory or transition to alternative solutions.

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

A: Yes, all substitute parts use the identical 16-SOIC package footprint and pinout. Existing PCB designs require no layout modifications for substitution.

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