SN74LS148D

Overview

The SN74LS148D is an 8-line-to-3-line priority encoder manufactured by Texas Instruments. It belongs to the 74LS logic family and utilizes a 16-pin SOIC surface-mount package. The device accepts eight active-low data inputs and encodes them into three active-low binary outputs, prioritizing higher-order inputs when multiple signals are present simultaneously. It operates on a single power supply ranging from 4.75V to 5.25V. Key control features include an Enable Input (EI) for cascading expansion and dedicated outputs for Group Select (GS) and Enable Output (EO).

Feature Summary

• Active-low encoding of eight input lines into three-bit binary codes with priority handling.
• Cascading capability through dedicated Enable Input, Enable Output, and Group Select pins.
• Buffered inputs designed to drive standard 74LS series loads.

Applications

• Keyboard encoding circuits
• Interrupt request management systems
• Data multiplexing applications

Procurement Notes

Verify that the specific suffix 'D' corresponds to the 16-SOIC package variant rather than PDIP or other formats. Confirm RoHS compliance status as manufacturing specifications may vary by production batch. Ensure the source document explicitly lists the SN74LS148D part number to avoid confusion with similar variants like SN74LS148DR or SN74LS148N.

Selection Notes

Select this component when an 8-input priority encoding function is required in a surface-mount design. The 74LS series offers defined propagation delays suitable for general digital logic timing requirements. Verify that the system voltage aligns with the specified 5V operating range and that the SOIC footprint matches the PCB layout constraints.

Part Context

This component is part of the broader 74LS148 family of priority encoders produced by Texas Instruments. While the base model SN74LS148 typically refers to the PDIP package, the 'D' suffix specifically identifies the SOIC surface-mount version. It shares identical logical functionality with other package variations within the same logic family.

Replacement Considerations

SN74LS148DR

FAQ

How does the SN74LS148D handle simultaneous input signals?

It functions as a priority encoder, meaning it only encodes the highest-order active input among any simultaneous signals.

What is the purpose of the GS pin?

The GS (Group Select) pin goes low when any valid input is being encoded, indicating that the output lines represent a valid code.