SN74ALS666DWR

Overview

The SN74ALS666DWR is an 8-bit D-type transparent latch with 3-state outputs, manufactured by Texas Instruments in a 24-pin Small-Outline (DW) package. It operates within a supply voltage range of 4.5 V to 5.5 V and supports an operating temperature range of 0°C to 70°C. The device features true logic outputs, allowing data from the input bus to be stored and read back onto the same bus via the OERB control input. Propagation delays for data inputs to outputs range from 3 ns to 18 ns depending on transition direction.

Feature Summary

• Provides 3-state I/O-type read-back inputs that allow stored data to pass back onto the input data bus when the read-back control is low.
• Features a bus-structured pinout design suitable for efficient utilization in bus-structured applications.
• Includes preset and clear inputs for direct control of latch states independent of the clock enable signal.

Applications

• Bus-structured memory storage systems
• Transparent data latching for input/output interfaces
• Read-back verification circuits

Procurement Notes

Verify the specific ordering suffix matches the required package variant. Confirm RoHS compliance status and lead finish details against the latest packaging addendum. Ensure the operating temperature range aligns with your system's environmental requirements. Check moisture sensitivity level ratings for proper handling during assembly processes.

Selection Notes

Select this component when true logic output polarity is required, as opposed to the inverted outputs found in the SN74ALS667. Consider the 24-pin SOIC package dimensions for PCB layout constraints. Evaluate the 3-state output current capabilities against bus loading requirements. Verify compatibility with existing ALS family logic levels and timing specifications.

Part Context

This part belongs to the SN74ALS666/667 family of 8-bit transparent latches. It shares functional similarities with the SN74ALS667 but differs in output logic polarity. Both devices utilize the same DW package options and share identical pinouts, differing only in whether the Q outputs provide true or inverted data relative to the D inputs.

Replacement Considerations

SN74ALS667DW serves as a logical substitute if inverted output logic is acceptable. SN74ALS666NT offers the same functionality in a standard plastic DIP package instead of the SOIC form factor. Cross-referencing with other ALS family latches requires verifying pin compatibility and electrical characteristics.