SN74HCT257DR

Overview

The SN74HCT257DR is a quadruple 2-line to 1-line data selector/multiplexer with 3-state outputs manufactured by Texas Instruments. It operates within a supply voltage range of 4.5 V to 5.5 V and features typical propagation delays of 17 ns at 5.5 V. The device provides high-current 3-state outputs capable of driving up to ±6 mA, ensuring direct interface with system buses. It includes buffered inputs and outputs, low power consumption with a maximum ICC of 80 µA, and TTL-voltage compatible inputs.

Feature Summary

• Provides four independent 2-to-1 multiplexing channels with shared address select lines
• Features 3-state outputs that interface directly with system buses without loading data lines when disabled
• Includes buffered inputs and outputs for improved signal integrity in bus-organized systems

Applications

• Multiplexing signals from multiple 4-bit data sources to output data lines
• Bus interface applications connecting multiple sources in high-performance systems
• Data selection circuits requiring direct interfacing with system buses

Procurement Notes

Verify the specific ordering suffix 'DR' corresponds to the SOIC-16 package and tape-and-reel configuration. Confirm RoHS compliance status and lead finish details via the manufacturer's official documentation before procurement. Ensure the operating temperature range meets the application requirements.

Selection Notes

Select this component for designs requiring HCT logic compatibility with standard TTL voltages. Verify that the 4.5 V to 5.5 V supply voltage range aligns with the system power rails. Consider the 3-state output capability if bus isolation or multi-driver configurations are necessary for the target architecture.

Part Context

This part belongs to the SN74HCT257 family of quadruple 2-line to 1-line data selectors. It is functionally related to other variants such as the SN74HC257 and SN74ALS257, differing primarily in logic family characteristics and speed specifications. The device serves as a core digital logic component for data routing tasks.

Replacement Considerations

SN74HCT257D (Tube packaging)

FAQ

How does the OE input affect the output state?

When the Output Enable (OE) input is High, the outputs enter a high-impedance state. When OE is Low, the selected data inputs (A or B) are passed to the outputs based on the A/B select line.

What is the recommended handling for unused inputs?

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