DS2127

Ultra3 LVD/SE SCSI 14-Line Terminator

Ultra3 LVD/SE SCSI 14-Line Terminator with Tightest V_REF Limits Available

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Overview

Fully Compliant with Ultra2, Ultra3, Ultra160, and Ultra320 SCSI Standards
Provides LVD/SE Termination for 14 Signal Pairs
Auto-Selection of LVD or SE Termination
5% Tolerance on SE and LVD Termination Resistance
Low 3pF Power-Down Capacitance
Built-In Mode-Change Filter/Delay
On-Board Thermal-Shutdown Circuitry
SCSI Bus Hot-Plug Compatible
Fully Supports Actively Negated SE SCSI Signals

The DS2127 Ultra3 LVD/SE SCSI terminator provides low-voltage differential (LVD)/single-ended (SE) terminations for 14 SCSI lines. Through the voltage on the DIFF_CAP pin, the device detects the types of drivers on the bus. If the device is connected in an LVD-only bus, the DS2127 provides LVD termination. If any single- ended devices are connected to the bus, the DS2127 uses SE termination. If any high-voltage differential (HVD) devices are connected to the bus, the DS2127 isolates itself from the SCSI bus. The mode change has a built-in delay that is determined by an integrated SPI-3 mode change filter/delay. The terminating resistors can also be disconnected from the bus by asserting the ISO pin.

For the LVD termination, the DS2127 provides 14 precisely trimmed resistors. Each resistor is biased with two current sources to a fail-safe state. For SE termination, the DS2127 provides 14 precision 110Ω resistors and one regulator for active-negation bias.

Applications