UCC5640PW24

Overview

The UCC5640PW24 is a low-voltage differential (LVD) active terminator designed for SCSI networks. It operates within a TRMPWR voltage range of 2.7 V to 5.25 V and supports an operating temperature range of 0°C to 70°C. The device provides a differential impedance of 105 Ω and a common-mode impedance of 150 Ω. It features a 24-pin TSSOP package with a maximum supply current of 25 mA under no-load conditions. The component includes a disconnect input that reduces disabled terminator supply current to 400 µA.

Feature Summary

• Active Y-terminator design optimized for LVD SCSI bus performance
• Automatic detection and switching between LVD, SE, and HVD modes
• Differential failsafe biasing to maintain signal integrity
• Low channel capacitance to minimize bus loading

Applications

• SCSI SPI-2 Ultra2 (Fast-40) bus termination
• SCSI SPI-3 Ultra3 / Ultra160 (Fast-80) bus termination
• SCSI SPI-4 (Fast-160) bus termination

Procurement Notes

Verify the specific ordering suffix when purchasing. The standard tube version is designated as UCC5640PW24, while the tape and reel variant requires the TR suffix (UCC5640PW24TR). Confirm the package type matches the intended PCB layout requirements before finalizing orders.

Selection Notes

Select this component specifically for Low Voltage Differential (LVD) SCSI applications. It is not suitable for Single Ended (SE) or High Voltage Differential (HVD) systems. Ensure the system power supply remains within the 2.7 V to 5.25 V range to guarantee proper regulator operation and mode detection thresholds.

Part Context

This device belongs to the UCC5640 family of active terminators manufactured by Texas Instruments. The PW24 designation indicates the 24-pin Thin Shrink Small Outline Package (TSSOP). A 28-pin variant (UCC5640PW28) exists, which includes additional pins for LVD status indication.

Replacement Considerations

Direct functional replacements include other UCC5640 variants such as the UCC5640PW28. Verify pin compatibility and package dimensions when substituting models to ensure correct board integration.

FAQ

How does the UCC5640 detect the bus type?

It monitors the DIFFSENS line voltage via the DIFFB pin. If the voltage is between 0.7 V and 1.9 V, it enters LVD mode. Voltages below 0.5 V or above 2.4 V trigger a high-impedance state for SE/HVD buses.

What are the required decoupling capacitors?

Both the TRMPWR and REG pins require a 4.7-µF capacitor and a 0.01-µF high-frequency, low ESR capacitor connected to ground.

Can this device be used in High Voltage Differential systems?

No. The UCC5640 is designed exclusively for LVD networks. In HVD systems, it detects the condition and automatically disconnects from the bus.