CD74HCT138M Equivalent & Substitute Parts

Part Overview

The CD74HCT138M is a 1 x 3:8 decoder/demultiplexer logic IC manufactured by Texas Instruments in a 16-SOIC surface mount package. This part is discontinued at DiGi Electronics, making equivalent substitutes necessary for ongoing production and maintenance applications. The device operates as a single-supply decoder with standard TTL-compatible logic levels, suitable for address decoding and multiplexing applications in digital systems.

Key Parameters

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

Substitute Part Grouping Explanation

Substitution of the CD74HCT138M is determined by strict equivalence in the following parameters:

Functional Type: Decoder/Demultiplexer with 1 x 3:8 circuit configuration
Output Current Specifications: 4mA high and 4mA low output current capability
Supply Voltage: 4.5V to 5.5V single supply operation
Package: 16-SOIC surface mount form factor
Base Product Number: 74HCT138 series designation

Substitute parts are grouped into three categories based on manufacturer and packaging variation:

Direct Manufacturer Equivalents – Same base part number with packaging or tape/reel variations
Parametric Equivalents – Alternative base numbers (74HCT238) with identical electrical specifications
Manufacturer-Recommended Alternatives – Cross-manufacturer parts meeting all electrical and mechanical requirements

Parameter Comparison

Part Number	Manufacturer	Output Current (mA)	Supply Voltage (V)	Temp Range (°C)	Package	Status
CD74HCT138M	Texas Instruments	4 / 4	4.5–5.5	-55 to 125	16-SOIC	Discontinued
CD74HCT138M96	Texas Instruments	4 / 4	4.5–5.5	-55 to 125	16-SOIC	Active
CD74HCT238M	Texas Instruments	4 / 4	4.5–5.5	-55 to 125	16-SOIC	Obsolete
MM74HCT138M	Fairchild Semiconductor	4.8 / 4.8	4.5–5.5	-40 to 85	16-SOIC	Active
74HCT138D,653	Nexperia USA Inc.	4 / 4	4.5–5.5	-40 to 125	16-SO	Active
74HCT138D-Q100,118	NXP USA Inc.	4 / 4	4.5–5.5	-40 to 125	16-SO	Active
74HCT138S16-13	Diodes Incorporated	4 / 4	4.5–5.5	-40 to 125	16-SO	Active
MC74HCT138ADR2G	onsemi	4 / 4	4.5–5.5	-55 to 125	16-SOIC	Active
MM74HCT138MX	Fairchild Semiconductor	4.8 / 4.8	4.5–5.5	-40 to 85	16-SOIC	Active

Engineering Selection Recommendations

Tier 1 – Direct Replacement (Highest Compatibility)

CD74HCT138M96 (Texas Instruments) is the primary substitute. It maintains identical electrical specifications and package form factor as the original part, with the distinction of active product status and tape & reel packaging. This part is recommended for applications requiring exact functional equivalence with maximum inventory availability.

Tier 2 – Electrical Equivalent with Extended Temperature Range

74HCT138D,653 (Nexperia USA Inc.), 74HCT138D-Q100,118 (NXP USA Inc.), and 74HCT138S16-13 (Diodes Incorporated) provide full electrical equivalence with operating temperature ranges extending to -40°C to 125°C. These parts use 16-SO packaging, which is mechanically compatible with 16-SOIC footprints. All three maintain ROHS3 compliance and MSL 1 rating. The 74HCT138D-Q100,118 variant includes AEC-Q100 automotive qualification for applications requiring automotive-grade components.

Tier 3 – Parametric Equivalents with Enhanced Output Current

MM74HCT138M and MM74HCT138MX (Fairchild Semiconductor) provide 4.8mA output current capability, exceeding the original 4mA specification. These parts are suitable for applications requiring higher drive capability. Operating temperature range is limited to -40°C to 85°C, making them appropriate for commercial and industrial environments but not extended military temperature applications.

Tier 4 – Alternative Base Number

MC74HCT138ADR2G (onsemi) and CD74HCT238M (Texas Instruments) are parametric equivalents with identical electrical performance. The onsemi part is active with full compliance certifications. The CD74HCT238M is obsolete and not recommended for new designs.

Frequently Asked Questions (FAQ)

Q: Can I use 74HCT138D,653 as a direct replacement for CD74HCT138M?

A: Yes. Both parts share identical decoder/demultiplexer functionality, 1 x 3:8 circuit configuration, 4mA output current, and 4.5V–5.5V supply voltage. The 16-SO package is mechanically compatible with 16-SOIC footprints. The primary difference is the narrower operating temperature range (-40°C to 125°C versus -55°C to 125°C), which is acceptable for most commercial and industrial applications.

Q: What is the difference between CD74HCT138M96 and CD74HCT138M?

A: Both are Texas Instruments 74HCT138 decoders with identical electrical specifications. CD74HCT138M96 is the active product variant supplied in tape & reel packaging, while CD74HCT138M is discontinued. The "96" suffix indicates tape & reel format. For new procurement, CD74HCT138M96 is the recommended choice.

Q: Are Fairchild MM74HCT138M and MM74HCT138MX interchangeable?

A: Both Fairchild parts provide identical 4.8mA output current and 4.5V–5.5V supply voltage. The primary difference is packaging format. Both are suitable for applications where the enhanced 4.8mA output current is beneficial. Operating temperature range is -40°C to 85°C for both variants.

Q: Does the 74HCT138D-Q100,118 variant offer any advantages?

A: Yes. The 74HCT138D-Q100,118 includes AEC-Q100 automotive qualification, making it suitable for automotive and mission-critical applications requiring automotive-grade component certification. Electrical specifications remain identical to standard 74HCT138D variants.

Q: Can I substitute CD74HCT238M for CD74HCT138M?

A: CD74HCT238M is a parametric equivalent with identical electrical specifications. However, it is listed as obsolete, making it unsuitable for new designs or long-term production. Active alternatives such as CD74HCT138M96 or MC74HCT138ADR2G are preferred.

Q: What packaging considerations apply when selecting a substitute?

A: The original CD74HCT138M uses 16-SOIC packaging. Direct substitutes maintain this package type. Alternatives such as 74HCT138D,653, 74HCT138D-Q100,118, and 74HCT138S16-13 use 16-SO packaging, which is mechanically compatible with 16-SOIC PCB footprints. Verify PCB layout compatibility before final selection.

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