SN74ALS667DWRG4

Overview

The SN74ALS667DWRG4 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 inverted Q outputs. The device operates within a supply voltage range of 4.5 V to 5.5 V and supports an operating temperature range from 0°C to 70°C. Key electrical parameters include a maximum propagation delay of 28 ns, a high-level output current of -2.6 mA, and a low-level output current of 24 mA. It is housed in a 24-pin Small-Outline (DW) package.

Feature Summary

• Provides true data storage via D inputs while simultaneously allowing stored data to be read back onto the input bus through the OERB control pin.
• Features dual independent output enable pins (OE1 and OE2) that place the Q outputs into a high-impedance state when asserted high.
• Includes dedicated preset and clear inputs for direct asynchronous control of the internal latch states.

Applications

• Bus-structured applications requiring bidirectional data transfer capabilities
• System designs needing simultaneous data latching and diagnostic read-back functions
• Memory interface circuits utilizing 3-state buffering

Procurement Notes

Verify the specific ordering suffix 'RG4' against the manufacturer's latest documentation to confirm compliance with RoHS directives and lead finish specifications. Ensure the procurement channel sources components matching the exact SN74ALS667DWRG4 designation to guarantee correct packaging and material attributes.

Selection Notes

Select this component when inverted logic levels are required for the Q outputs compared to the D inputs. It is suitable for systems requiring read-back verification of stored data without external circuitry. Compare performance metrics such as propagation delay and output drive strength against alternative logic families if higher speed or different voltage compatibility is needed.

Part Context

This part is a member of the SN74ALS66x family, which includes the SN74ALS666 variant featuring non-inverting outputs. Both devices share identical pinouts and functional descriptions regarding the read-back mechanism and 3-state control, differing only in the polarity of the Q outputs relative to the D inputs.

Replacement Considerations

The SN74ALS667DW serves as a standard production equivalent. Verify package dimensions and pin configurations before substitution to ensure mechanical compatibility on existing printed circuit boards.

FAQ

How does the read-back function operate?

When the read-back control (OERB) input is taken 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 controls the 3-state output condition?

The Q outputs enter a high-impedance state if either of the output-enable inputs (OE1 or OE2) is at a high logic level.