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.
The DS2127 is a dual-mode active terminator designed for 14-line SCSI buses. It automatically detects the bus mode (LVD, SE, or HVD) via the DIFF_CAP pin and switches its internal circuitry accordingly to provide appropriate termination resistors. In LVD mode, it offers precise differential and common-mode resistance with fail-safe biasing. In SE mode, it provides single-ended termination with active negation bias.
| Operating Temperature Range | 0°C to +70°C |
|---|---|
| LVD Differential-Mode Termination Resistance | 100 Ω typical |
| Supply Current (LVD Mode) | 32 mA typical |
| Thermal-Shutdown Threshold | 130 °C |
The device is fully compliant with Ultra2, Ultra3, Ultra160, and Ultra320 SCSI Standards.
It detects the types of drivers on the bus through the voltage on the DIFF_CAP pin.
Yes, by asserting the ISO pin, the terminating resistors can be disconnected from the SCSI bus.