MC74ACT138D

Overview

The MC74ACT138D is a high-speed 1-of-8 decoder/demultiplexer from the 74ACT logic series. It accepts three binary weighted address inputs (A0, A1, A2) and provides eight mutually exclusive active-LOW outputs (O0-O7). The device operates within a supply voltage range of 4.5 V to 5.5 V. It features TTL-compatible inputs and outputs capable of sourcing or sinking 24 mA. The package is SOIC-16.

Feature Summary

• Features multiple input enables for easy parallel expansion to larger decoding configurations
• Provides active-low mutually exclusive outputs for precise signal selection
• Includes demultiplexing capability by utilizing enable inputs as data paths

Applications

• High-speed bipolar memory chip select address decoding
• Parallel expansion to 1-of-24 or 1-of-32 decoders
• General-purpose 8-output demultiplexing

Procurement Notes

Verify that the specific part number matches the required logic family suffix. Confirm the package type corresponds to the design requirements. Check RoHS compliance documentation if lead-free materials are mandated. Ensure the operating temperature range aligns with the system environment. Validate pinout compatibility during integration.

Selection Notes

Select this component when TTL-compatible inputs are required alongside AC speed performance. Consider the 24 mA output drive capability for direct load interfacing. Evaluate the need for multiple enable inputs to simplify system expansion architectures. Verify power supply constraints fit the 4.5 V to 5.5 V operational window.

Part Context

This device belongs to the MC74AC/ACT138 family of 1-of-8 decoders. It shares functional similarities with the standard AC variant but offers distinct input threshold characteristics suitable for TTL interfaces. The D suffix indicates the SOIC-16 surface mount packaging format used in this specific ordering code.

Replacement Considerations

MC74ACT138DR2

FAQ

How does the MC74ACT138D handle input signals?

It accepts three binary weighted address inputs (A0, A1, A2) which determine the active output line.

What is the function of the enable inputs?

The device has three enable inputs; two are active-LOW and one is active-HIGH, allowing for device enabling and system expansion.