74AC138PC Equivalent & Substitute Parts

Part Overview

The 74AC138PC is a decoder/demultiplexer integrated circuit manufactured by onsemi, designed for 1 x 3:8 logic decoding applications. This component features a 16-pin DIP package and operates across a 2V to 6V supply voltage range with output currents of 24mA for both high and low states. The product is classified as obsolete, making identification of functionally equivalent alternatives essential for ongoing system maintenance, legacy design support, and component procurement.

Substiute Parts

74AC138PC

onsemiIn Stock: 226274AC138PC Datasheet

Current PartRFQ

CD74AC138E

Harris CorporationIn Stock: 1604CD74AC138E Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the 74AC138PC is determined by strict alignment with the following critical parameters:

• Circuit Configuration: Must be 1 x 3:8 decoder/demultiplexer topology
• Package Type: Must be 16-DIP (0.300", 7.62mm) for mechanical and pin compatibility
• Mounting Method: Must support through-hole installation
• Output Current Capability: Must provide minimum 24mA output drive for both high and low states
• Voltage Supply Compatibility: Substitute supply range must encompass or exceed the original 2V ~ 6V specification
• Logic Family: Must be 74AC series to ensure timing and electrical characteristics alignment

The CD74AC138E meets all substitution criteria through identical circuit configuration, package geometry, mounting type, and output current specifications. The substitute part's expanded voltage range (1.5V ~ 5.5V) and extended operating temperature range (-55°C ~ 125°C) provide additional operational flexibility while maintaining full functional equivalence.

Parameter Comparison

Engineering Selection Recommendations

The CD74AC138E represents a direct functional equivalent to the 74AC138PC based on identical decoder/demultiplexer circuit topology, package geometry, and electrical output specifications. Both components share obsolete product status, indicating limited ongoing manufacturer support and potential supply constraints.

Selection between these parts should prioritize availability and procurement lead time, as both components are classified as obsolete. The CD74AC138E offers operational advantages through an extended temperature range (-55°C ~ 125°C versus -40°C ~ 85°C), which may provide benefits in applications requiring broader environmental tolerance. However, the overlapping voltage supply range (1.5V ~ 5.5V) requires verification that system supply voltages remain within this common operating window.

Compliance considerations are equivalent between both parts: both carry EAR99 export classification and identical HTSUS coding. The CD74AC138E is classified as RoHS non-compliant, consistent with the obsolete status of both components and typical for legacy logic devices of this generation.

Frequently Asked Questions (FAQ)

Q: Can the CD74AC138E be used as a direct replacement for the 74AC138PC in existing designs?

A: Yes. Both components share identical circuit configuration (1 x 3:8 decoder/demultiplexer), package type (16-DIP), mounting method (through-hole), and output current specifications (24mA). Pin-for-pin compatibility is assured. Verify that system supply voltage remains within the overlapping range of 1.5V ~ 5.5V.

Q: What is the significance of the different voltage supply ranges?

A: The 74AC138PC operates from 2V ~ 6V, while the CD74AC138E operates from 1.5V ~ 5.5V. The overlapping range is 1.5V ~ 5.5V. If your system operates at voltages below 1.5V or above 5.5V, neither component is suitable. If your system operates between 1.5V and 5.5V, both are compatible.

Q: Are there differences in operating temperature ranges?

A: Yes. The 74AC138PC operates from -40°C ~ 85°C, while the CD74AC138E operates from -55°C ~ 125°C. The CD74AC138E provides extended temperature capability. If your application requires operation below -40°C or above 85°C, the CD74AC138E is the appropriate choice within the overlapping voltage range.

Q: Why are both components classified as obsolete?

A: Both the 74AC138PC and CD74AC138E are legacy logic devices from the 74AC family. Obsolete status indicates that manufacturers have discontinued active production and support. Component availability is limited to existing inventory from distributors and secondary markets.

Q: Are there any compliance or regulatory differences between these parts?

A: Both components carry identical ECCN (EAR99) and HTSUS (8542.39.0001) classifications. The CD74AC138E is RoHS non-compliant, which is typical for obsolete logic devices predating RoHS requirements. Compliance requirements should be evaluated based on your application's regulatory environment and end-use classification.

Q: What should I verify before implementing a substitution?

A: Confirm that your system's supply voltage operates within the 1.5V ~ 5.5V overlapping range. Verify that the through-hole 16-DIP package is compatible with your PCB design and assembly process. Confirm that the operating temperature range of your application falls within -55°C ~ 125°C (CD74AC138E) or -40°C ~ 85°C (74AC138PC). Validate component availability and procurement lead times, as both are obsolete.