CD74HCT138MT Equivalent & Substitute Parts

Part Overview

The CD74HCT138MT is a Decoder/Demultiplexer logic IC manufactured by Texas Instruments, featuring a 1 x 3:8 circuit configuration in a 16-SOIC surface mount package. This part is classified as Obsolete, making identification of functionally equivalent alternatives essential for design continuity and procurement planning. Substitute parts must maintain identical electrical performance characteristics and package compatibility to ensure direct replacement capability in existing circuit designs.

Key Parameters

Parameter	Value
Manufacturer Part Number	CD74HCT138MT
Manufacturer	Texas Instruments
Type	Decoder/Demultiplexer
Circuit Configuration	1 x 3:8
Current - Output High, Low	4mA, 4mA
Voltage Supply	4.5V ~ 5.5V
Operating Temperature	-55°C ~ 125°C
Package / Case	16-SOIC (0.154", 3.90mm Width)
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level	1 (Unlimited)

Substitute Part Grouping Explanation

Substitute parts for the CD74HCT138MT are qualified based on the following critical parameters that determine functional equivalence:

Circuit configuration: 1 x 3:8 decoder/demultiplexer topology
Output current capability: 4mA minimum for both high and low states
Supply voltage range: 4.5V to 5.5V single supply operation
Operating temperature range: Minimum -55°C to 125°C coverage
Package type: 16-SOIC surface mount with 0.154" width (3.90mm)
Compliance: ROHS3 and REACH requirements

Substitute parts are categorized as Parametric Equivalents (matching all electrical and mechanical specifications) or Manufacturer Recommended alternatives (functionally compatible with minor parameter variations acceptable for the application class).

Parameter Comparison

Part Number	Manufacturer	Product Status	Circuit	Output Current (mA)	Supply Voltage	Temp Range (°C)	Package	RoHS
CD74HCT138MT	Texas Instruments	Obsolete	1 x 3:8	4, 4	4.5-5.5V	-55 to 125	16-SOIC	ROHS3
CD74HCT137M96	Texas Instruments	Active	1 x 3:8	4, 4	4.5-5.5V	-55 to 125	16-SOIC	ROHS3
CD74HCT137MT	Texas Instruments	Last Time Buy	1 x 3:8	4, 4	4.5-5.5V	-55 to 125	16-SOIC	ROHS3
CD74HCT138M96	Texas Instruments	Active	1 x 3:8	4, 4	4.5-5.5V	-55 to 125	16-SOIC	ROHS3
CD74HCT238M96	Texas Instruments	Active	1 x 3:8	4, 4	4.5-5.5V	-55 to 125	16-SOIC	ROHS3
74HCT138D,653	Nexperia USA Inc.	Active	1 x 3:8	4, 4	4.5-5.5V	-40 to 125	16-SOIC	ROHS3
74HCT138S16-13	Diodes Incorporated	Active	1 x 3:8	4, 4	4.5-5.5V	-40 to 125	16-SOIC	ROHS3
MM74HCT138M	Fairchild Semiconductor	Active	1 x 3:8	4.8, 4.8	4.5-5.5V	-40 to 85	16-SOIC	Not specified
MM74HCT138MX	Fairchild Semiconductor	Active	1 x 3:8	4.8, 4.8	4.5-5.5V	-40 to 85	16-SOIC	Not specified
MC74HCT138ADR2G	onsemi	Active	1 x 3:8	4, 4	4.5-5.5V	-55 to 125	16-SOIC	ROHS3

Engineering Selection Recommendations

Preferred Substitutes (Full Parametric Equivalence):

CD74HCT138M96, CD74HCT137M96, CD74HCT238M96, and MC74HCT138ADR2G are direct parametric equivalents to the CD74HCT138MT. These parts maintain identical electrical specifications, operating temperature range (-55°C to 125°C), output current ratings (4mA), and package configuration. All are ROHS3 compliant and carry Active product status, ensuring long-term availability and supply chain stability.

Alternative Substitutes (Acceptable for Most Applications):

74HCT138D,653 (Nexperia) and 74HCT138S16-13 (Diodes Incorporated) are manufacturer-recommended alternatives with Active status. These parts meet all electrical and package requirements but operate over a narrower temperature range (-40°C to 125°C). Selection of these alternatives is appropriate for applications where the extended low-temperature performance of the original part is not required.

Conditional Substitutes (Verify Application Requirements):

MM74HCT138M and MM74HCT138MX (Fairchild Semiconductor) provide higher output current capability (4.8mA) and are functionally compatible. However, these parts operate over a reduced temperature range (-40°C to 85°C) and lack specified RoHS certification. Use these alternatives only when the narrower temperature range and higher current capability align with application requirements.

Frequently Asked Questions (FAQ)

Q: Can CD74HCT138M96 directly replace CD74HCT138MT without circuit modification?

A: Yes. CD74HCT138M96 is a parametric equivalent with identical electrical specifications, output current ratings, supply voltage range, and operating temperature range. The 16-SOIC package dimensions are identical, enabling direct PCB footprint compatibility.

Q: What is the difference between CD74HCT137M96 and CD74HCT138M96?

A: Both parts are 1 x 3:8 decoder/demultiplexers with identical electrical characteristics and package specifications. The primary difference is the base product number designation (74HCT137 versus 74HCT138), which reflects internal logic configuration differences. Consult device datasheets to confirm functional equivalence for your specific application.

Q: Why do some substitutes have a narrower operating temperature range?

A: The 74HCT138D,653 and 74HCT138S16-13 operate from -40°C to 125°C, compared to the original part's -55°C to 125°C range. These alternatives are suitable for applications operating within the -40°C to 125°C window. Applications requiring extended low-temperature performance below -40°C must use parts with the full -55°C to 125°C specification.

Q: Are MM74HCT138M and MM74HCT138MX suitable replacements?

A: These Fairchild parts provide higher output current (4.8mA versus 4mA) and are functionally compatible. However, they operate only to -40°C minimum and lack RoHS certification documentation. Use these alternatives only when application requirements permit the narrower temperature range and when RoHS compliance is not mandated.

Q: What packaging options are available for substitutes?

A: All qualified substitutes are supplied in 16-SOIC surface mount packages with 0.154" (3.90mm) width, matching the original CD74HCT138MT package. Packaging format variations (Tape & Reel, Cut Tape, Digi-Reel) do not affect electrical or mechanical compatibility; these represent supply chain options only.

Q: Is ROHS3 compliance required for my application?

A: ROHS3 compliance is mandatory for applications subject to European Union Restriction of Hazardous Substances regulations. CD74HCT138M96, CD74HCT137M96, CD74HCT238M96, MC74HCT138ADR2G, 74HCT138D,653, and 74HCT138S16-13 all carry ROHS3 certification. MM74HCT138M and MM74HCT138MX do not specify RoHS status and should not be used in applications requiring this compliance.

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