SN74AS257DR

Overview

The SN74AS257DR is a quad 2-to-1 data selector/multiplexer from the Texas Instruments AS logic series, housed in a 16-pin SOIC package. It operates on a single supply voltage ranging from 4.5 V to 5.5 V with a nominal value of 5 V. The device features four independent multiplexing circuits, each selecting between two data inputs (A and B) based on a common select line (A/B). Outputs are controlled by an output-enable (OE) input, providing three-state capability for bus interfacing. The component supports high-level output currents up to -15 mA and low-level output currents up to 48 mA.

Feature Summary

• Provides four independent channels for selecting between dual data sources
• Features three-state outputs that isolate data lines when disabled
• Supports direct interface with system buses in high-performance architectures

Applications

• Multiplexing signals from multiple data sources to shared output lines
• Bus organization systems requiring signal selection
• High-performance digital systems utilizing 3-state bus interfaces

Procurement Notes

Verify the specific ordering suffix 'DR' corresponds to the tape-and-reel packaging format rather than tube packaging. Confirm the active production status and lead times directly with Texas Instruments or authorized distributors, as availability may vary. Ensure the procurement documentation matches the exact part number SN74AS257DR to guarantee correct package type and reel specifications.

Selection Notes

Select this component for applications requiring fast switching speeds within the AS logic family compared to standard TTL or ALS variants. Consider the 16-pin SOIC surface-mount package for PCB space efficiency. Verify that the required operating temperature range aligns with the commercial specification of 0°C to 70°C, as military-grade versions utilize different suffixes.

Part Context

This device belongs to the SN74AS257 family of data selectors. It shares functional similarities with the SN74ALS257 but offers higher speed performance characteristics typical of the AS series. The 'D' suffix indicates the plastic small-outline package, while 'R' denotes the reel packaging configuration used for automated assembly processes.

Replacement Considerations

SN74AS257D

FAQ

How does the OE input affect the output state?

When the output-enable (OE) input is at a high logic level, the three-state outputs enter a high-impedance state, effectively disconnecting them from the data lines.

What determines which data input is selected?

The A/B select input determines the source; a low level selects inputs A, while a high level selects inputs B for all four multiplexer channels simultaneously.