SN74HC138D

Overview

The SN74HC138D is a 3-to-8 decoder and demultiplexer manufactured by Texas Instruments in a 16-pin SOIC package. It operates within a supply voltage range of 2 V to 6 V and supports an operating temperature from -40°C to +85°C. The device features three binary select inputs (A, B, C) and three enable inputs (G1, G2A, G2B). Outputs are active-low, with one selected output pulled low while others remain high. Electrical characteristics include a maximum propagation delay of 45 ns at 4.5 V, ±4 mA output drive capability, and a maximum ICC of 80 µA.

Feature Summary

• Designed for high-speed memory decoding and data-routing applications requiring short propagation delays.
• Incorporates three enable inputs to simplify cascading or data reception without external inverters.
• Outputs can drive up to 10 LSTTL loads, ensuring compatibility with standard logic families.

Applications

• LED Displays
• Servers
• White Goods

Procurement Notes

Verify the specific ordering suffix against the manufacturer's current Package Option Addendum, as the base SN74HC138D designation may indicate obsolete status depending on the carrier type. Confirm RoHS compliance and lead finish specifications directly from the latest datasheet revision to ensure alignment with assembly requirements.

Selection Notes

Select this component when a 3-to-8 decoding function is required with CMOS input levels and active-low outputs. Ensure the system voltage falls within the 2 V to 6 V range and that the thermal resistance of the SOIC package meets the application's heat dissipation needs under the specified ambient temperature conditions.

Part Context

This part belongs to the SNx4HC138 family of 3-line to 8-line decoders and demultiplexers. It utilizes high-speed silicon gate CMOS technology, offering performance comparable to low-power Schottky TTL while maintaining low power consumption typical of CMOS devices. The device is intended for use in systems where minimal decoding delay is critical.

Replacement Considerations

SN74HC138DR

FAQ

How many enable inputs does the SN74HC138D have?

The device has three enable inputs: one active-high (G1) and two active-low (G2A and G2B).

What is the state of unselected outputs?

When enabled, the selected output is pulled LOW, while all remaining unselected outputs remain HIGH.