DM74AS640N

Overview

The DM74AS640N is an octal bus transceiver manufactured by Fairchild Semiconductor, belonging to the Advanced Schottky (AS) logic family. It features eight bidirectional data paths with true outputs and is housed in a 20-pin plastic dual-in-line package (PDIP). The device operates within a supply voltage range of 4.5V to 5.5V and supports a commercial operating temperature range of 0°C to 70°C. Designed for high-speed applications, it utilizes an oxide-isolated, ion-implanted Schottky TTL process to deliver improved switching performance while maintaining functional and pin compatibility with standard 74LS and Schottky counterparts.

Feature Summary

• Provides bidirectional data transmission between two buses controlled by direction and enable inputs
• Features true outputs suitable for direct interfacing with system buses
• Utilizes advanced oxide-isolated, ion-implanted Schottky TTL process for enhanced speed and lower power dissipation

Applications

• Memory systems requiring high-speed data transfer
• Microprocessor-based architectures utilizing bidirectional data buses
• Asynchronous communication interfaces

Procurement Notes

Verify component authenticity as this part may be obsolete or discontinued. Confirm that the 20-pin PDIP package matches your PCB footprint requirements. Ensure the 4.5V to 5.5V supply voltage aligns with your system design. Check for lead-free compliance if required by current environmental regulations. Validate that the commercial temperature range meets your operational environment needs.

Selection Notes

Select this component when designing systems requiring octal bidirectional data transfer with true output polarity. It serves as a suitable replacement for older 74LS640 designs where higher speed is necessary. Consider the 20-pin DIP package constraints during layout planning. Verify that the input/output voltage levels are compatible with the connected CMOS or TTL devices in the target application circuit.

Part Context

This device belongs to the Fairchild DM74AS series, which represents the Advanced Schottky logic family known for superior speed-power trade-offs compared to standard Schottky logic. The DM74AS640 variant specifically provides octal bus transceiver functionality with true outputs, distinguishing it from inverting variants like the DM74AS646. It shares the same physical package and pinout as other members of the AS-240/244/640 families, facilitating modular design approaches.

Replacement Considerations

Consider SN74AS640N from Texas Instruments as a parameter-equivalent substitute. Verify that any alternative maintains the same octal configuration, true output polarity, and 20-pin PDIP package dimensions to ensure mechanical and electrical compatibility.