74LCX646MSA

Overview

The onsemi 74LCX646MSA is a low-voltage octal bus 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 logic environments. The device provides multiplexed transmission of data directly from input buses or internal storage registers. Key electrical specifications include a maximum propagation delay of 7.0ns at 3.3V, a quiescent supply current of 10µA, and output drive capabilities 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 data storage and real-time transmission between two octal buses.
• Features 5V tolerant inputs and outputs, allowing safe interfacing between low-voltage (2.5V/3.3V) systems and 5V signal environments.
• Supports live insertion and withdrawal operations when configured correctly, enabling dynamic bus management without system shutdown.
• Implements patented noise and EMI reduction circuitry while maintaining CMOS low power dissipation and high-speed operation.

Applications

• Multiplexed data transmission in low-voltage memory architectures
• Bus-oriented communication systems requiring 5V tolerance
• Live insertion/withdrawal peripheral interfaces

Procurement Notes

Verify the specific package variant, as the 74LCX646 is available in SOIC, SSOP, and TSSOP configurations. Confirm that the ordering code matches the required pinout and physical dimensions for your PCB layout. Ensure compatibility with the 2.3V to 3.6V operating voltage range for your target application environment.

Selection Notes

Select this component for applications requiring bidirectional data transfer between 8-bit buses with optional latching. It is suitable for designs needing 5V tolerance on both inputs and outputs while powered by lower voltages. Consider the 24-lead SSOP package for space-constrained surface-mount assemblies requiring shrink small outline dimensions.

Part Context

This device belongs to the LCX family of low-voltage CMOS logic integrated circuits. It combines the speed of AC/ACT families with the low power consumption of LVC/LCX technologies. The part serves as an octal transceiver/register, distinct from simple buffers or inverters, offering complex control over data flow direction and storage states.

Replacement Considerations

Direct substitutes may include other octal bus transceivers with 5V tolerance such as the SN74LVC646 or similar LCX-family equivalents. Verify pin compatibility and electrical characteristics like propagation delay and output drive current before substitution.

FAQ

How does the device handle data during power-up or power-down?

The device features power-down high impedance inputs and outputs. To ensure the high-impedance state during these transitions, the OE pin should be tied to VCC through a pull-up resistor.

What is the maximum clock frequency supported by the 74LCX646?

The maximum clock frequency is specified as 150 MHz under recommended operating conditions.

Can the A and B buses be driven simultaneously?

No, only one of the two busses, A or B, may be driven at a time. The direction control (DIR) input determines which bus receives data when the output enable (OE) is active.