DM74ALS240ASJ

Overview

The DM74ALS240ASJ is an octal 3-STATE bus driver manufactured by onsemi (Fairchild) in the 74ALS logic series. It utilizes an advanced low power oxide-isolated ion-implanted Schottky TTL process and features a PNP input design to reduce loading. The device provides two groups of four buffers with separate enable gating, symmetrically enabled when set logic LOW. It includes 3-STATE circuitry that maintains outputs in a high impedance state during power supply ramp-up or ramp-down to eliminate bus glitching. The component operates within a supply voltage range of 4.5V to 5.5V and supports a low level drive current of 24mA.

Feature Summary

• Octal 3-STATE bus drivers designed for flexible implementation in memory, microprocessor, or communication systems.
• Functional and pin compatible with the DM74LS counterpart while offering improved switching performance and less power dissipation.
• Switching response specifications are guaranteed over the full temperature and VCC supply range.
• PNP input design reduces input loading compared to standard TTL counterparts.

Applications

• Bus interface implementation with memory systems
• Bus interface implementation with microprocessor systems
• Bus interface implementation with communication systems

Procurement Notes

Verify the specific ordering suffix 'SJ' corresponds to the 20-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide as defined in the official datasheet. Confirm the manufacturer origin, as this part was originally produced by Fairchild Semiconductor and may now be distributed under the onsemi brand. Ensure compatibility with existing PCB footprints designated for package number M20D before procurement.

Selection Notes

Select the DM74ALS240ASJ when an octal 3-STATE buffer with non-inverting logic is required for ALS-level speed and power characteristics. This component is suitable for designs needing symmetric enable gating controlled by a single active-low signal per group of four outputs. Consider the SOP-20 package constraints if space is limited, and verify that the 24mA low-level output drive meets the load requirements of the destination circuits.

Part Context

This component belongs to the DM74ALS240A/DM74ALS241A family of Octal 3-STATE Bus Drivers. While the DM74ALS240A enables outputs symmetrically when control inputs are set logic LOW, the DM74ALS241A variant features complementary enable gating. Both share the same physical package options and core switching characteristics but differ in their logical enable behavior.

Replacement Considerations

SN74ALS240A-1N (Texas Instruments)

FAQ

How does the DM74ALS240ASJ handle power supply transitions?

The 3-STATE circuitry contains a feature that maintains the buffer outputs in a high impedance state during power supply ramp-up or ramp-down, which eliminates bus glitching problems that typically arise during these events.

What is the function of the G control inputs?

The G control inputs symmetrically enable the respective outputs when set to logic LOW. When the input is HIGH or the device is disabled, the outputs enter a high impedance state.