74LCX646MSAX

Overview

The onsemi 74LCX646MSAX is a low-voltage octal transceiver and register featuring 5V tolerant inputs and outputs. It operates within a supply voltage range of 2.3V to 3.6V, supporting interfaces with 5V signal environments. The device provides multiplexed transmission of data directly from the input bus or internal storage registers. Key electrical parameters include a maximum propagation delay of 7.0ns at 3.3V, a quiescent supply current of 10µA, and an output drive capability of ±24mA at 3.0V. It supports live insertion/withdrawal and implements patented noise reduction circuitry.

Feature Summary

• Provides registered bus transceiver functionality with D-type flip-flops for multiplexed data transmission between buses A and B.
• Features 5V tolerant inputs and outputs, enabling safe interfacing between low-voltage logic and 5V signal environments.
• Supports live insertion and withdrawal operations when configured correctly, ensuring high-impedance states during power transitions.

Applications

• Bus management systems requiring real-time transfer and stored mode data handling
• Low-voltage applications interfacing with 5V signal environments
• Systems supporting live insertion and withdrawal protocols

Procurement Notes

Verify the specific package variant, as the MSAX suffix denotes the SSOP-24 form factor. Confirm that the design accounts for the required pull-up resistor on the OE pin to ensure proper high-impedance behavior during power cycles. Check for RoHS compliance status and lead-free availability in current production runs.

Selection Notes

Select this component for designs requiring bidirectional data flow with optional latching capabilities. Ensure the operating voltage aligns with the 2.3V to 3.6V specification. Consider the 5V tolerance feature if connecting to legacy 5V buses. Verify that the 24-pin SSOP package fits the available PCB footprint and thermal requirements.

Part Context

This part belongs to the LCX family of low-voltage CMOS logic devices. It combines the functions of a bus transceiver and a register, offering flexibility in data path configuration. The device is designed for high-speed operation while maintaining low power dissipation, making it suitable for portable and battery-operated electronics.

Replacement Considerations

Direct substitutes may include other octal bus transceivers with 5V tolerance from manufacturers such as Texas Instruments or Nexperia. Verify pin compatibility and electrical specifications before substitution.

FAQ

How does the device handle data transmission between Bus A and Bus B?

Data can be transmitted in real-time (transparent mode) or stored in internal registers. The direction control (DIR) and select (SAB, SBA) inputs determine whether data flows from A to B, B to A, or is isolated.

What is the purpose of the OE pin connection during power-up?

To ensure the high-impedance state during power up or down, the OE pin should be tied to VCC through a pull-up resistor. This prevents unintended data driving during the power transition phase.