SN74ALS667DW

Overview

The SN74ALS667DW is an 8-bit D-type transparent read-back latch with 3-state outputs manufactured by Texas Instruments. It belongs to the ALS logic series and features inverting logic, where Q outputs provide the inverse of the data applied to its D inputs. The device operates within a supply voltage range of 4.5 V to 5.5 V and supports an operating free-air temperature range from 0°C to 70°C. It utilizes a 24-pin Small-Outline (DW) package. Key electrical characteristics include a propagation delay time of up to 20 ns, a low-level output current capability of 24 mA, and a high-level output current of -2.6 mA.

Feature Summary

• Provides 3-state I/O-type read-back inputs for reading stored data onto the input data bus via the OERB control pin.
• Features a bus-structured pinout design suitable for bus-structured applications.
• Includes preset and clear inputs for direct control of latch states.

Applications

• Storing contents of an input data bus
• Reading back stored data onto the input data bus
• Bus-structured applications

Procurement Notes

Verify that the specific orderable part number matches the required suffix, such as SN74ALS667DW or SN74ALS667DW.A, as both are listed as active production items. Confirm the package type is SOIC (DW) with 24 pins and check the RoHS compliance status, which is indicated as Yes. Ensure the operating temperature range meets the application requirements of 0°C to 70°C before finalizing procurement.

Selection Notes

Select this component when an 8-bit transparent latch with inverted outputs and 3-state capabilities is required. It is appropriate for designs needing read-back functionality on the input bus. Compare it against the non-inverting SN74ALS666 if true outputs are preferred instead. Consider the ALS series speed and power characteristics relative to other logic families for the specific system constraints.

Part Context

This device is part of the SN74ALS666/667 family of 8-bit D-type transparent read-back latches with 3-state outputs. It shares functional similarities with the SN74ALS666 but differs in logic polarity, providing inverted outputs. Both devices are designed for storing input data bus contents and reading them back, utilizing a bus-structured pinout for efficient integration into digital systems.

Replacement Considerations

The SN74ALS666DW serves as a direct alternative if non-inverting (true) outputs are required instead of the inverted outputs provided by the SN74ALS667DW. Both share identical pinouts, packaging, and core read-back functionality within the ALS logic family.

FAQ

How does the read-back feature function?

Read-back is controlled by the OERB input. When OERB is low, the data present at the output of the data latches passes back onto the input data bus. When OERB is high, the latch outputs are isolated from the D inputs.

What is the difference between SN74ALS666 and SN74ALS667?

The primary difference is the logic polarity. The SN74ALS666 provides true (non-inverting) outputs, while the SN74ALS667 provides inverted outputs relative to the D inputs.