DM74ALS138MX Equivalent & Substitute Parts

Part Overview

The DM74ALS138MX is a Decoder/Demultiplexer logic integrated circuit manufactured by onsemi, featuring a 1 x 3:8 configuration in a 16-SOIC package. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The part operates with single supply voltage between 4.5V and 5.5V, suitable for standard TTL logic applications requiring decoding or demultiplexing functions.

Substiute Parts

DM74ALS138MX

onsemiIn Stock: 1943DM74ALS138MX Datasheet

Current PartRFQ

SN74ALS138AD

Texas InstrumentsIn Stock: 2021SN74ALS138AD Datasheet

DirectRFQ

SN74ALS138ADR

Texas InstrumentsIn Stock: 1934SN74ALS138ADR Datasheet

DirectRFQ

SN74ALS138ANSR

Texas InstrumentsIn Stock: 3463SN74ALS138ANSR Datasheet

SimilarRFQ

SN74AS138DR

Texas InstrumentsIn Stock: 2024SN74AS138DR Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the DM74ALS138MX is determined by strict equivalence across the following critical parameters:

• Logic Series Compatibility: 74ALS series parts maintain functional and electrical equivalence
• Circuit Configuration: 1 x 3:8 decoder/demultiplexer topology
• Electrical Specifications: Voltage supply range (4.5V ~ 5.5V), output current ratings (400µA high, 8mA low), and operating temperature range (0°C ~ 70°C)
• Package Type: 16-SOIC surface mount package with matching pin configuration
• Functional Performance: Identical decoder/demultiplexer operation

Substitute parts are categorized as follows:

Direct Manufacturer Substitutes (Texas Instruments 74ALS series): SN74ALS138AD, SN74ALS138ADR maintain full electrical and functional equivalence with identical package specifications.

Similar Configuration Substitute (Texas Instruments 74ALS series, alternate package width): SN74ALS138ANSR provides functional equivalence with a 16-SO package (0.209" width) instead of the standard 0.154" width, requiring PCB layout verification.

Parametric Equivalent (Texas Instruments 74AS series): SN74AS138DR offers electrical equivalence within the same package but operates in the faster 74AS logic family, suitable where speed performance is acceptable or beneficial.

Parameter Comparison

Engineering Selection Recommendations

Primary Recommendation: SN74ALS138ADR (Texas Instruments) is the preferred substitute. This part maintains active product status, provides ROHS3 compliance, and offers identical electrical and package specifications to the DM74ALS138MX. The Cut Tape and Digi-Reel packaging format supports both prototype and production volume requirements.

Secondary Recommendation: SN74ALS138AD (Texas Instruments) provides direct functional equivalence with identical package dimensions. This part carries Last Time Buy status, indicating limited future availability. Selection is appropriate for designs where immediate procurement is necessary and long-term supply is not critical.

Alternative for Expanded Availability: SN74ALS138ANSR (Texas Instruments) offers the same functional performance and active product status. The 16-SO package features a wider body (0.209" versus 0.154"), requiring verification that PCB footprint spacing accommodates the increased width. This part provides the highest inventory availability among active substitutes.

Parametric Alternative: SN74AS138DR operates in the faster 74AS logic family while maintaining electrical compatibility within the specified voltage and current parameters. This part is discontinued at DiGi Electronics and should be selected only when speed performance requirements exceed 74ALS capabilities and alternative sourcing is confirmed.

Frequently Asked Questions (FAQ)

Q: Can SN74ALS138ANSR be used as a direct replacement on existing PCBs designed for DM74ALS138MX?

A: SN74ALS138ANSR requires PCB layout verification. The 16-SO package body width is 0.209 inches compared to the standard 0.154 inches for 16-SOIC. If the PCB footprint was designed with standard 0.154" spacing, the wider package may not fit without layout modification. Pin configuration and electrical function remain identical.

Q: What is the difference between 74ALS and 74AS logic series?

A: Both series operate within the same voltage supply range (4.5V ~ 5.5V) and output current specifications. The 74AS series provides faster propagation delay characteristics. For the DM74ALS138MX decoder function, 74AS substitution is electrically compatible but introduces faster switching behavior, which may require timing analysis in speed-critical applications.

Q: Why is the DM74ALS138MX classified as obsolete?

A: Obsolete status indicates the manufacturer (onsemi) has discontinued production. Active substitutes from Texas Instruments (SN74ALS138ADR, SN74ALS138ANSR) provide equivalent functionality with ongoing manufacturing support and compliance certifications.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All Texas Instruments substitutes listed carry ROHS3 compliance certification. The original DM74ALS138MX RoHS status was not specified in available documentation.

Q: Which substitute offers the best long-term availability?

A: SN74ALS138ADR maintains active product status from Texas Instruments, providing the most reliable long-term supply chain. SN74ALS138ANSR also carries active status with higher current inventory levels (3400 pcs), though package width verification is required for PCB compatibility.