UCC5670MWP

Overview

The UCC5670MWP is a SCSI multimode active terminator manufactured by Texas Instruments in a 36-pin MWP package. It supports Single-Ended (SE) and Low-Voltage Differential (LVD) termination to bridge transitions between SCSI parallel interface standards SPI-2, SPI-3, and SPI-4. The device operates on a TERMPWR supply ranging from 2.7 V to 5.25 V. Electrical characteristics include an LVD mode supply current of 35 mA typical and an SE mode supply current of 21 mA typical. The differential impedance is specified at 105 Ω typical, while the single-ended impedance is 108 Ω typical. The output capacitance for both modes is 3 pF.

Feature Summary

• Supports automatic selection between Single-Ended (SE), Low-Voltage Differential (LVD), and High-Power Differential (HIPD) termination modes based on bus voltage detection.
• Complies with SCSI-1, SCSI-2, SCSI-3 SPI, Ultra, Ultra2, Ultra3/Ultra160, and Ultra320 standards.
• Integrates differential fail-safe bias and thermal packaging designed for low junction temperature and improved MTBF.
• Pin-compatible with the UCC5630A, allowing for digital SPI-3 mode changes and filter delay adjustments.

Applications

• Active termination for SCSI bus segments requiring coexistence of SE and LVD devices.
• Bridging legacy Single-Ended SCSI systems to modern Low-Voltage Differential implementations.
• High-speed data transfer environments supporting Ultra2, Ultra3/Ultra160, and Ultra320 specifications.

Procurement Notes

Verify the specific ordering suffix when sourcing components. The base model UCC5670MWP is supplied in a tube, whereas the R suffix variant indicates a taped and reeled configuration intended for quantities of 1000 devices per reel. Confirm package type requirements against manufacturing equipment capabilities before procurement.

Selection Notes

Select this component for designs requiring a monolithic solution to manage mixed-mode SCSI environments. Ensure the design accommodates the 36-pin MWP package dimensions and thermal dissipation requirements. Verify that the system power supply remains within the 2.7 V to 5.25 V operating range to maintain proper regulator functionality and termination accuracy.

Part Context

This device belongs to the UCC5670 family of SCSI terminators produced by Texas Instruments. It serves as a specialized interface component designed to handle the electrical requirements of parallel SCSI buses during technology transitions. The MWP package provides the necessary pin count and thermal management for multi-line termination applications.

Replacement Considerations

The UCC5630A is documented as a pin-compatible alternative within the same product family. Designers may consider this substitute if specific SPI-3 mode change or filter delay characteristics differ from the UCC5670MWP requirements.

FAQ

How does the UCC5670 determine the active termination mode?

The device monitors the DIFFSENS control line via the DIFFB input pin. Voltages below 0.5 V trigger Single-Ended mode, voltages between 0.7 V and 1.9 V trigger Low-Voltage Differential mode, and voltages above 2.4 V trigger High-Power Differential mode.

What is the function of the DISCNCT pin?

The DISCNCT pin controls the connection state of the terminator. Pulling it to ground activates the terminator (connect mode), while leaving it open or pulling it high disables the termination regulators and switches lines to high impedance (disconnect mode).

Why are multiple UCC5670 ICs required per SCSI bus end?

Three ICs are required at each end of a SCSI bus segment to terminate the full set of 27 lines, comprising 18 data lines and 9 control lines.