DM74ALS257SJX

Overview

The DM74ALS257SJX is a quad 1-of-2-line data selector/multiplexer manufactured by onsemi, formerly Fairchild Semiconductor. It features true outputs and operates within a supply voltage range of 4.5 V to 5.5 V. The device utilizes an advanced oxide-isolated, ion-implanted Schottky TTL process. Propagation delay from data inputs to outputs ranges from 2 ns to 12 ns depending on the transition direction. Output enable times are specified between 4 ns and 18 ns. The component is housed in a 16-Lead Small Outline Package (SOP) with a width of 5.3 mm.

Feature Summary

• Contains four independent multiplexers that route a 4-bit word from one of two sources to three-state outputs.
• Outputs present true data levels to minimize propagation delay time compared to inverted counterparts.
• Three-state buffer-type outputs allow direct interfacing with bus lines without additional drivers.
• Functionally and pin-for-pin compatible with standard Schottky and low power Schottky TTL devices.

Applications

• Multiplexing dual data buses in microprocessor systems
• Implementing n-bit data selectors for bus-organized systems
• Source programming counters

Procurement Notes

Verify the ordering code suffix 'X' corresponds to tape and reel packaging as specified in the datasheet. Confirm the package designation matches the SOP variant rather than SOIC or PDIP. Ensure the manufacturer origin aligns with onsemi or its predecessor entity, Fairchild Semiconductor, given corporate acquisitions. Check RoHS compliance status against current regulatory requirements.

Selection Notes

Select this component when true logic output polarity is required for specific timing constraints. The ALS series offers improved AC performance over standard Schottky logic while maintaining compatibility. Verify that the 5.3mm wide SOP footprint fits the target PCB layout. Consider the DM74ALS258 if inverted outputs are acceptable for the design.

Part Context

This part belongs to the DM74ALS family of logic integrated circuits. It serves as a data selector within the broader category of encoders, decoders, and multiplexers. The device is designed for use in memory and microprocessor systems requiring bidirectional data transfer capabilities via its three-state outputs.

Replacement Considerations

The DM74ALS258M is a functional substitute offering inverted outputs instead of true outputs. Other variants include the DM74ALS257N in a PDIP package and the DM74ALS257M in an SOIC package. Cross-reference with SN74ALS257AN from Texas Instruments for equivalent functionality in different packaging.

FAQ

What is the difference between the DM74ALS257 and DM74ALS258?

The DM74ALS257 provides true data outputs, whereas the DM74ALS258 provides inverted data outputs to the four three-state outputs.

How does the 'X' suffix affect the component?

Appending the letter 'X' to the ordering code indicates that the device is available in tape and reel packaging.

Can multiple DM74ALS257 units be paralleled?

Yes, the three-state output feature allows up to 258 sources to be implemented for data buses by paralleling n-bit data selectors.