SN74AS138D

Overview

The SN74AS138D is a high-speed silicon-gate CMOS 3-to-8 line decoder/demultiplexer manufactured by Texas Instruments. It operates within a supply voltage range of 2V to 6V and supports data rates up to 100MHz. The device features Schottky-clamped inputs for high performance and includes two active-low and one active-high enable inputs. It is housed in a 16-pin SOIC package with an operating temperature range of -55°C to 125°C.

Feature Summary

• High-speed operation with propagation delays as low as 10ns at 5V
• Schottky-clamped inputs provide high noise immunity and performance
• Flexible enable logic with two active-low and one active-high control inputs

Applications

• Address decoding for memory systems
• Demultiplexing data streams
• Generating multiple chip select signals

Procurement Notes

Verify the specific suffix 'D' confirms the SOIC-16 surface-mount package variant. Confirm RoHS compliance status if required for your assembly process. Check for any automotive or industrial qualification markings if applicable to your environment. Ensure the manufacturer source is verified against official Texas Instruments documentation.

Selection Notes

Select this component when high-speed switching and robust noise immunity are required. The AS series offers superior speed compared to standard LS or ALS counterparts. Verify that the 2V to 6V supply range aligns with your system's power rails. Consider the 16-pin SOIC footprint for PCB layout compatibility.

Part Context

This part belongs to the Texas Instruments 74AS (Advanced Schottky) logic family, known for its high speed and low power consumption relative to earlier generations. It serves as a direct functional replacement for other 3-to-8 decoders in legacy designs requiring faster transition times.

Replacement Considerations

Compatible substitutes include SN74ALS138D and SN74LS138D, though these offer slower speeds. SN74F138D provides similar functionality with different electrical characteristics. Verify pinout compatibility before substitution.