UCC5680PW28TR

Overview

The UCC5680PW28TR is a low-voltage differential (LVD) Small Computer System Interface (SCSI) terminator manufactured by Texas Instruments. It operates within a supply voltage range of 2.7 V to 5.25 V and supports an operating temperature range of 0°C to 70°C. The device is housed in a 28-pin Thin Shrink Small-Outline Package (TSSOP, PW). It integrates a mode change delay function required by the SPI-3 specification and automatically disconnects from the bus if single-ended or high-voltage differential drivers are detected. Electrical characteristics include a typical differential impedance of 105 Ω and a common-mode bias voltage of 1.25 V.

Feature Summary

• Integrates built-in mode change delay filter for SPI-3 compliance
• Automatically detects and disconnects from SE or HVD SCSI buses
• Provides precise differential termination with internal impedance trimming

Applications

• Low-voltage differential SCSI bus termination
• SPI-3 compliant system implementations
• Ultra2, Ultra3/Ultra160, and Ultra320 SCSI interface protection

Procurement Notes

Verify that the ordering suffix TR indicates the taped and reeled packaging format containing 2000 devices per reel. Confirm the specific package variant matches the 28-pin TSSOP designation. Ensure the component status is listed as active for new designs. Cross-reference the manufacturer part number against official documentation to confirm compatibility with the intended application requirements.

Selection Notes

Select this component specifically for LVD-only SCSI environments where automatic detection of incompatible driver types is necessary. The 28-pin package provides an additional LVD status output pin compared to the 24-pin version. Ensure the design accommodates the required 100 ms to 300 ms mode change delay period during power-up or bus transitions.

Part Context

This device belongs to the UCC5680 family of SCSI terminators designed to manage bus termination states dynamically. It replaces fixed termination networks by sensing the DIFFSENS line voltage to determine the presence of LVD, SE, or HVD drivers. The family includes variants such as the UCC5680PW24 and UCC5680PW28, differentiated primarily by pin count and available status outputs.

Replacement Considerations

UCC5680PW28G4

FAQ

How does the UCC5680 handle the presence of Single-Ended or High-Voltage Differential drivers?

If the device detects an SE or HVD driver via the DIFFB input threshold, it switches all terminating resistors off the bus and enters a high-impedance state to prevent bus interference.

What is the purpose of the DISCNCT pin?

The DISCNCT pin allows manual control to shut down the terminator. When active (high), it switches off the terminating resistors and both voltage regulators to save power.

What are the recommended decoupling capacitor values for the TRMPWR and REG pins?

A 4.7-µF capacitor and a high-frequency, low-ESR 0.01-µF capacitor should be installed close to both the TRMPWR and REG pins.