DM74S240J

Overview

The DM74S240J is an octal 3-state buffer and line driver manufactured by National Semiconductor. It operates within a supply voltage range of 4.75V to 5.25V and features dual 4-bit configurations in a 20-pin DIP package. The device provides inverted outputs with high-impedance states controlled by enable inputs. It supports propagation delays of up to 10ns at 5V with 150pF load and delivers output currents of 15mA (high) and 64mA (low). Operating temperatures range from 0°C to 70°C.

Feature Summary

• Provides bidirectional or unidirectional buffering for memory, microprocessor, and communication systems
• Features low impedance outputs capable of driving terminated transmission lines down to 133 ohms
• High input impedance prevents significant loading of the transmission line
• Includes eight 3-state buffers organized with four buffers sharing a common enable gate

Applications

• Memory system interface buffering
• Microprocessor bus driving
• Communication system signal routing

Procurement Notes

Verify component authenticity as National Semiconductor was acquired by Texas Instruments. Confirm package integrity and pin alignment for 20-DIP compatibility. Check datasheet revisions for electrical parameter updates. Ensure environmental compliance matches original specifications. Validate supplier documentation against official manufacturer records.

Selection Notes

Select this component for applications requiring fast switching speeds and low power dissipation compared to standard Schottky TTL. Ensure circuit design accommodates the specific output current capabilities and transmission line termination requirements. Verify that the inverted output polarity aligns with system logic requirements.

Part Context

This part belongs to the Advance Schottky (AS) logic family, designed for improved switching performance. It is functionally and pin-compatible with 74LS and standard Schottky counterparts. The device is part of a series including non-inverting variants like the DM74AS244.

Replacement Considerations

Public confirmed substitute part numbers include SN74AS240AN from Texas Instruments. Verify pinout and electrical characteristics match before substitution.