DM74AS646NT

Overview

The DM74AS646NT is an octal bus transceiver and register manufactured by onsemi in the 74AS logic series. It features totem-pole 3-STATE outputs designed for driving highly-capacitive or low-impedance loads directly without interface components. The device incorporates edge-triggered D-type flip-flops that store input data on positive clock transitions. It supports real-time and stored data transfer between buses A and B, controlled by enable (G) and direction (DIR) pins. Operating conditions include a supply voltage range of 4.5V to 5.5V and a free air operating temperature of 0°C to +70°C.

Feature Summary

• Incorporates an octal bus transceiver with an octal D-type register for multiplexed transmission.
• Features totem-pole 3-STATE outputs capable of driving bus lines directly without pull-up components.
• Includes select controls with a make-before-break configuration to eliminate glitches during data transitions.
• Functionally and pin-for-pin compatible with LS TTL counterparts.

Applications

• Implementing buffer registers
• I/O ports
• Bidirectional bus drivers
• Working registers

Procurement Notes

Verify component authenticity through authorized channels as this part may be subject to obsolescence. Confirm package integrity upon receipt, specifically checking for damage to the 24-Lead Plastic Dual-In-Line Package. Ensure compatibility with existing system voltage levels and temperature requirements before integration. Review current datasheets for any updates regarding recommended operating conditions.

Selection Notes

Select this component when designing systems requiring direct bus interfacing with storage capabilities. It is suitable for applications needing high-drive outputs for capacitive loads. Consider the 74AS series speed characteristics and power consumption relative to other logic families. Verify that the 24-PDIP package fits the available PCB space and manufacturing constraints.

Part Context

This device belongs to the Fairchild Semiconductor DM74AS646/648 family, now under onsemi. It is part of the Advanced Schottky TTL logic series, known for high-speed performance. The NT suffix indicates the 24-Lead Plastic Dual-In-Line Package. This specific model provides non-inverting functionality, unlike the DM74AS648 which stores and transfers complemented data.

Replacement Considerations

SN74AS641FN-00 is listed as a parameter equivalent from Texas Instruments.