SN74HCT138PW

Overview

The SN74HCT138PW is a 3-line to 8-line decoder/demultiplexer manufactured by Texas Instruments. It operates within a supply voltage range of 4.5 V to 5.5 V and supports an operating temperature range from -40 °C to +85 °C. The device features three binary-select inputs (A, B, C) and three enable inputs (G1, G2A, G2B). Propagation delay times are specified at 45 ns maximum for the A, B, or C inputs to any output at 4.5 V, and 34 ns maximum at 5.5 V. The package type is TSSOP-16.

Feature Summary

• Designed for high-performance memory-decoding and data-routing applications requiring short propagation delays.
• Incorporates three enable inputs to simplify cascading and demultiplexing functions without external inverters.
• Inputs are TTL-voltage compatible with low input current characteristics.

Applications

• High-speed memory decoding systems
• Data transmission routing
• Demultiplexing applications

Procurement Notes

Verify the specific ordering suffix against the manufacturer's latest Package Option Addendum to confirm production status and material specifications. The SN74HCT138PW variant may be listed as obsolete in some documentation while the tape-and-reel version remains active. Confirm RoHS compliance and moisture sensitivity level ratings directly from the datasheet before procurement.

Selection Notes

Select this component when TTL-compatible logic levels are required alongside HCT speed performance. Ensure the design accommodates the 4.5 V to 5.5 V supply voltage constraints. Verify that the TSSOP-16 package dimensions fit the target PCB layout and thermal requirements. Consider the enable pin configuration if system expansion beyond eight outputs is planned.

Part Context

This device belongs to the SNx4HCT138 family of 3-line to 8-line decoders and demultiplexers. It is part of the broader 74HCT logic series designed for CMOS technology with TTL-compatible inputs. Other variants in this family include SOIC, PDIP, and CDIP packages, offering flexibility for different mounting styles and thermal environments.

Replacement Considerations

SN74HCT138PWR

FAQ

How many enable inputs does the SN74HCT138PW have?

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

What is the typical propagation delay time for this device?

The typical propagation delay time (tpd) is 17 ns.