CD74HCT138M

Overview

The CD74HCT138M is a high-speed CMOS logic device manufactured by Harris Corporation, functioning as a 3-to-8 line decoder and demultiplexer. It operates within a supply voltage range of 4.5V to 5.5V and utilizes an HCT series technology compatible with LSTTL inputs. The component features three binary address inputs (A0, A1, A2) and three enable inputs (two active-low, one active-high) to facilitate cascading. It provides eight inverted outputs in a 16-pin Small Outline package.

Feature Summary

• Provides three binary address inputs for selecting one of eight decoded outputs
• Includes three enable inputs to manage device activation and simplify cascading configurations
• Features inverted outputs suitable for memory address decoding or data routing applications

Applications

• Memory address decoding systems
• Data routing circuits
• I/O port selection interfaces

Procurement Notes

Verify the manufacturer origin carefully, as Harris Corporation's semiconductor assets were acquired by Texas Instruments. Confirm that the specific unit matches the original Harris specifications rather than subsequent TI revisions. Check for lead-free compliance markings if RoHS adherence is required for the assembly process.

Selection Notes

Select this component when direct compatibility with LSTTL logic levels is necessary due to its HCT input structure. Ensure the application requires inverted outputs; otherwise, consider the non-inverting CD74HC238 variant. Verify that the operating environment stays within the specified temperature range and voltage limits for reliable performance.

Part Context

This part belongs to the CD74HC/HCT138 family of high-speed silicon-gate CMOS decoders. These devices are designed to offer low power consumption typical of CMOS technology while maintaining speeds comparable to Low-Power Schottky TTL logic. The family includes both inverting and non-inverting output options.

Replacement Considerations

CD74HCT138 (Texas Instruments equivalent)

FAQ

What is the logic level compatibility of the CD74HCT138M?

The HCT series inputs are directly compatible with LSTTL logic levels, allowing it to interface with standard 5V TTL systems.

How many enable inputs does the CD74HCT138M have?

It has three enable inputs: two active-low and one active-high, which allow for flexible cascading of multiple decoders.