74AC138SC

Overview

The Fairchild Semiconductor 74AC138SC is a high-speed CMOS logic device belonging to the 74AC series. It functions as a 1-of-8 decoder or demultiplexer, featuring three binary select inputs and three enable inputs to decode one active-low output from eight available lines. The component operates within a supply voltage range of 2 V to 6 V and supports surface-mount installation in a 16-pin SOIC package. Designed for industrial applications, it maintains reliable performance across an operating temperature range of -40°C to +85°C.

Feature Summary

• Provides decoding of three binary select inputs into one of eight mutually exclusive active-low outputs
• Incorporates three enable inputs (two active-low, one active-high) to facilitate system expansion without external gates
• Features fully buffered inputs with Schottky clamping to suppress line-ringing and simplify system design

Applications

• High-performance memory decoding systems
• Data routing and transmission systems
• Demultiplexing applications where enable inputs serve as data lines

Procurement Notes

Verify the manufacturer designation carefully, as Fairchild Semiconductor's logic division was acquired by onsemi. Ensure the specific part number matches the required package style and voltage specifications. Confirm RoHS compliance status through official documentation before procurement. Cross-reference datasheets to ensure compatibility with existing system requirements.

Selection Notes

Select this component when requiring high-speed decoding capabilities within the 74AC logic family. Consider the 16-pin SOIC package for surface-mount assembly needs. Evaluate the three-enable input configuration for complex cascading requirements. Verify that the 2V to 6V supply range aligns with the target circuit design parameters.

Part Context

This device belongs to the broader 74AC logic family, known for high-speed operation and wide voltage tolerance. Similar parts include the 74ACT138 for TTL-compatible interfaces and the 74HC138 for standard CMOS applications. The 74AC series offers superior speed compared to legacy HC variants while maintaining low power consumption suitable for modern digital designs.

Replacement Considerations

Direct substitutes include the MC74AC138SC manufactured by onsemi following the acquisition of Fairchild's semiconductor business. Other compatible alternatives within the same logic family are the 74ACT138SC and 74HC138SC, provided interface voltage levels and package dimensions match the original design constraints.