DS2118MB/T&R

Overview

The DS2118MB/T&R is a multimode SCSI terminator supporting LVD and SE termination for nine signal line pairs. It operates at 5V with a temperature range of 0°C to +70°C in a 36-pin SSOP package. The device features 5% tolerance on termination resistance, low power-down capacitance of 3pF, and onboard thermal shutdown. It provides autoselection between LVD and SE modes based on bus voltage sensing.

Feature Summary

• Multimode operation enabling automatic selection between Low-Voltage Differential (LVD) and Single-Ended (SE) termination modes.
• Supports SCSI SPI-2, SPI-3, SPI-4, Ultra160, and Ultra320 standards compliance.
• Integrates onboard thermal shutdown circuitry and hot-plug compatibility for the SCSI bus.

Applications

• Termination for SCSI bus signal lines in server and storage systems.
• Legacy SE device backward compatibility in modern LVD SCSI environments.
• High-speed data transfer interfaces requiring Ultra160 or Ultra320 compliance.

Procurement Notes

Verify the specific ordering suffix matches the required packaging format. Confirm that the component meets RoHS compliance requirements if applicable to the assembly process. Ensure the operating temperature range aligns with the system's environmental specifications before finalizing procurement decisions.

Selection Notes

Select this component when designing SCSI interfaces requiring simultaneous support for both LVD and legacy SE devices. Verify that the system provides adequate TERMPWR voltage within the specified limits. Consider the physical placement near the SCSI connector to minimize signal reflections and trace length effects.

Part Context

This part belongs to the DS2118M family of Ultra3 LVD/SE SCSI terminators manufactured by Analog Devices Inc./Maxim Integrated. The 'T&R' suffix indicates the unit is supplied in tape and reel packaging suitable for automated surface-mount assembly processes.

Replacement Considerations

DS2118MB

FAQ

How does the DS2118MB/T&R determine whether to use LVD or SE termination?

The device automatically senses the voltage on the SCSI bus DIFFSENS line. If the voltage indicates an LVD-only bus, it uses LVD termination; if any SE devices are present, it switches to SE termination.

What is the function of the ISO pin on the DS2118MB/T&R?

When pulled high, the ISO pin isolates the termination pins from the SCSI bus while keeping VREF active and maintaining bus mode indicators. An internal pulldown resistor ensures normal termination if the pin is left floating.

What capacitor values are recommended for the TPWR and VREF pins?

A 2.2µF capacitor and a 0.01µF high-frequency capacitor are recommended between TPWR and ground. A 4.7µF capacitor is required between the VREF pin and ground.