DS21T05Z+T&R

Overview

The DS21T05Z+T&R is a SCSI terminator IC compliant with SCSI-1, Fast SCSI, and Ultra SCSI standards. It provides active termination for nine signal lines using laser-trimmed 110-ohm resistors with 5% tolerance. The device operates on a TERMPWR supply voltage ranging from 4.0V to 5.5V. It features a low dropout regulator capable of sourcing at least 24 mA per line when active and sinking 200 mA for actively negated signals. The unit includes onboard thermal shutdown circuitry and a power-down mode that isolates termination resistors from the bus via the PD pin. It is housed in a 16-pin narrow SOIC package.

Feature Summary

• Fully compliant with SCSI-1, Fast SCSI, and Ultra SCSI standards
• Integrates nine precise-switched 110-ohm termination resistors
• Supports actively negated SCSI signals with high sink current capability
• Includes power-down mode for hot-plug compatibility and bus isolation

Applications

• Active termination for single-ended SCSI cable segments
• Disk drive interface circuits
• RAID system component interfaces

Procurement Notes

Verify the specific suffix T&R indicates tape-and-reel packaging configuration. Confirm RoHS compliance status through official manufacturer documentation or authorized distributor declarations. Ensure the ordering part number matches the exact package width (150-mil) required for the target PCB footprint. Cross-reference the manufacturer designation to confirm Analog Devices Inc./Maxim Integrated origin.

Selection Notes

Select this component for applications requiring active termination compatible with SCSI-1, Fast SCSI, and Ultra SCSI protocols. It serves as a functionally compatible alternative to the DS21T07, offering relaxed output current and termination tolerances suitable for high-volume designs. Ensure the design accommodates the 16-pin narrow SOIC package dimensions and provides adequate decoupling capacitors on the VREF and TERMPWR pins.

Part Context

The DS21T05Z+T&R belongs to the DS21T05 family of SCSI terminators manufactured by Analog Devices Inc./Maxim Integrated. It is designed to replace discrete resistor networks with an integrated solution that simplifies board layout and improves noise immunity. The device integrates a bandgap reference and buffer amplifier to maintain stable termination voltages under varying load conditions.

Replacement Considerations

The DS21T07 is a functionally compatible higher-performance alternative. Verify if the relaxed termination tolerances of the DS21T05 meet specific system requirements before substituting.