DM74LS138N

Overview

The DM74LS138N is a 3-to-8 line decoder/demultiplexer manufactured by onsemi in a 16-pin PDIP package. It operates within a supply voltage range of 4.75 V to 5.25 V and supports an operating temperature range of 0°C to +70°C. The device features three binary select inputs (A, B, C) and three enable inputs (G1, G2A, G2B). Propagation delays from select inputs to outputs range from 18 ns to 40 ns depending on the transition direction and load capacitance.

Feature Summary

• Incorporates Schottky clamping for high-performance operation and reduced line-ringing.
• Features fully buffered inputs presenting only one normalized load to the driving circuit.
• Includes two active-low and one active-high enable inputs to simplify cascading without external inverters.

Applications

• High-performance memory decoding systems
• Data routing applications requiring short propagation delay times
• Expansion of decoders to implement larger configurations such as 24-line or 32-line decoders

Procurement Notes

Verify component authenticity through authorized channels due to potential availability issues. Confirm that the specific ordering code matches the required package type and suffix. Check current lifecycle status as older logic families may be discontinued. Ensure environmental compliance requirements align with project specifications before finalizing procurement decisions.

Selection Notes

Select this component when low power dissipation and high speed are required for memory decoding tasks. The LS logic family offers a balance between performance and power consumption. Verify that the system voltage remains within the specified 4.75 V to 5.25 V range. Consider the PDIP package constraints if surface mount alternatives like the M variant are needed for different assembly processes.

Part Context

This part belongs to the 74LS series of digital logic integrated circuits, specifically designed for decoder and demultiplexer functions. It is part of a broader family including variants like the DM74ALS138N and MC74AC138N, which offer different speed and voltage characteristics. The DM74LS138N is historically significant for its use in standard TTL-compatible designs requiring efficient address decoding.

Replacement Considerations

The DM74LS138M serves as a pin-compatible alternative in a SOIC package. Other logical equivalents include the DM74ALS138N for higher speed or MC74AC138N for wider voltage ranges. Verify electrical compatibility and package dimensions when substituting these parts in existing designs.