SN74AHCT138N

Signal Switches, Multiplexers, Decoders Overview

The SN74AHCT138N is a 3-line to 8-line decoder/demultiplexer from the Texas Instruments AHCT logic family, housed in a 16-pin PDIP package. It operates within a supply voltage range of 1.5 V to 5.5 V and supports an operating temperature range of -40°C to +85°C. The device features TTL-compatible inputs and provides three enable inputs (one active-high G1, two active-low G2A/G2B) for simplified cascading. Electrical characteristics include a maximum propagation delay of 12 ns at 5 V with 15 pF load, and output drive capabilities of ±8 mA.

Signal Switches, Multiplexers, Decoders Feature Summary

• TTL-voltage compatible inputs ensure seamless integration with legacy logic systems.
• Three dedicated enable inputs facilitate complex cascading configurations without external inverters.
• High-speed performance optimized for high-performance memory decoding applications.

Signal Switches, Multiplexers, Decoders Applications

• High-performance memory decoding systems
• Data-routing and transmission systems
• Demultiplexing applications

Signal Switches, Multiplexers, Decoders Procurement Notes

Verify the specific ordering suffix 'N' corresponds to the PDIP-16 package configuration. Confirm RoHS compliance status and lead finish details via the latest Package Option Addendum. Ensure the procurement channel sources production-active parts, as some alternative packages may be obsolete.

Signal Switches, Multiplexers, Decoders Selection Notes

Select this component when TTL input compatibility is required alongside CMOS low power consumption. The AHCT series bridges the gap between older TTL standards and modern CMOS processes. Consider the PDIP package only if through-hole mounting is strictly necessary for the mechanical design constraints.

Signal Switches, Multiplexers, Decoders Part Context

This part belongs to the SNx4AHCT138 family, which includes variants in SOIC, SSOP, TSSOP, and VQFN packages. The 'SN74' prefix denotes commercial grade temperature ratings, while 'AHCT' specifies the high-speed CMOS technology with TTL-compatible inputs. Other family members share identical logical functionality but differ in physical footprint and thermal characteristics.

Signal Switches, Multiplexers, Decoders Replacement Considerations

Direct pin-compatible substitutes include SN74AHCT138DR (SOIC), SN74AHCT138PWR (TSSOP), and SN74AHCT138DBR (SSOP). Verify that the replacement package meets the board's mechanical and thermal requirements.

Signal Switches, Multiplexers, Decoders FAQ

How are the enable inputs configured for operation?

The device requires G1 to be High and both G2A and G2B to be Low for any output to be active. If these conditions are not met, all outputs remain High.

What is the recommended handling procedure for unused inputs?

All unused inputs must be connected to either VCC or GND to prevent undefined operational states caused by floating voltages.