M74HCT640B1R

Overview

The M74HCT640B1R is an obsolete octal bus transceiver with inverted 3-state outputs, manufactured by STMicroelectronics. It operates on a 4.5V to 5.5V supply voltage and features symmetrical output impedance with a minimum drive capability of 6mA for both high and low states. The device provides balanced propagation delays, typically 13ns at 4.5V, and maintains low power dissipation with a maximum quiescent current of 4μA. It includes protection circuits against static discharge and transient excess voltage on all inputs.

Feature Summary

• Octal bidirectional data transmission between two buses controlled by direction and enable inputs
• Inverted 3-state outputs compatible with standard TTL logic levels
• Symmetrical output impedance ensuring consistent drive strength in both directions

Applications

• Two-way asynchronous communication between data buses
• Data bus isolation when the device is disabled
• Directional control of data flow in digital systems

Procurement Notes

This component is officially marked as obsolete by the manufacturer. Verify availability through secondary distributors or authorized surplus channels. Confirm that the specific package variant matches your board design requirements before procurement. Ensure compliance with RoHS standards if applicable to your project specifications.

Selection Notes

Select this component only if its specific inverted output polarity aligns with system logic requirements. Consider the 3-state functionality for bus sharing applications. Evaluate the operating temperature range and supply voltage constraints against your environmental conditions. Check for pin compatibility with existing designs requiring 8-bit wide data paths.

Part Context

The M74HCT640 belongs to the HCT series of advanced high-speed CMOS logic devices. It is functionally compatible with the 74 Series 640 standard. The B1R suffix indicates a Plastic DIP-20 package configuration. This part represents a legacy solution for octal bus interfacing in older electronic architectures.

Replacement Considerations

Direct substitutes include CD74HCT640E from Texas Instruments. Other compatible options may be found within the same HCT series family from different manufacturers, provided pinouts and electrical characteristics match.