DS2118MB+

Overview

The DS2118MB+ is a multimode SCSI terminator supporting LVD and SE termination for nine signal line pairs. It complies with SPI-2, SPI-3, SPI-4, Ultra160, and Ultra320 standards. The device operates on a 5V supply within a 0°C to +70°C temperature range. It features a 36-pin SSOP package (0.300" width). Electrical parameters include an SE termination resistance of 110Ω typical, an LVD differential termination resistance of 110Ω typical, and an output capacitance of 3pF. The part includes thermal shutdown circuitry at 150°C and supports actively negated SE signals.

Feature Summary

• Autoselects between LVD and SE termination modes based on bus voltage sensing.
• Provides isolation from the SCSI bus when HVD devices are detected or during thermal shutdown.
• Supports actively negated single-ended SCSI signals with active pull-up capability.

Applications

• SCSI bus termination in systems requiring backward compatibility with legacy SE devices.
• Ultra320 and Ultra160 SCSI interface implementations.
• Multimode SCSI environments where LVD and SE devices coexist on the same bus.

Procurement Notes

Verify the specific ordering suffix (+) confirms lead-free and RoHS compliance as indicated in the manufacturer's documentation. Confirm the package type matches the required 36-SSOP form factor. Check current availability status as this component may be discontinued or subject to limited production runs. Ensure the operating temperature range meets the environmental requirements of the target application.

Selection Notes

Select this component for designs requiring automatic mode switching between low-voltage differential and single-ended SCSI signaling. Ensure the design accommodates the 36-pin SSOP footprint and provides adequate thermal management given the internal shutdown threshold. Verify that the system power supply can maintain the required 5V tolerance for proper regulator operation and termination resistance accuracy.

Part Context

The DS2118M series serves as a specialized interface solution for Small Computer System Interface applications. It bridges the transition period between legacy single-ended architectures and modern low-voltage differential standards. The device integrates precision resistor strings and control logic to manage impedance matching across multiple signal pairs without external configuration.

Replacement Considerations

DS2118MB

FAQ

How does the DS2118MB+ determine which termination mode to use?

The device uses internal DIFFSENSE circuitry to monitor the SCSI bus DIFFSENS line voltage. If the voltage indicates an LVD environment, it applies LVD termination; if it detects SE devices, it switches to SE termination automatically.

What happens if an HVD device is connected to the bus?

The DS2118MB+ identifies the presence of an HVD device via the DIFFSENS voltage level and isolates its termination pins from the SCSI bus to prevent damage or signal interference.

Is the DS2118MB+ compatible with actively negated SE drivers?

Yes, the device fully supports actively negated SE SCSI signals. In SE mode, the power amplifier can sink up to 22mA per line while maintaining the voltage reference regulation.