DESCRIPTION
The DS21T09 is intended for one-chip Plug and Play (PnP) SCSI termination. Plug and Play SCSI requires the exit-point terminator on computer motherboards or host bus adapters to automatically switch off if an external device is connected to the system. The DS21T09 satisfies this requirement by offering the engineer a choice of onboard current sensing circuitry or onboard ground detect circuitry. If an external device is connected, the DS21T09 will automatically be isolated from the SCSI bus thereby maintaining proper system termination.

FEATURES
■ Fully compliant with SCSI-1, Fast SCSI and Ultra SCSI
■ Compatible with Plug and Play SCSI Profile
■ Functional drop in replacement for the DS2109
■ Complementary part to DS21T07 for wide SCSI
■ Provides active termination for 18 signal lines
■ 2% tolerance on termination resistors and voltage regulator
■ Bus termination sensing
■ Low power-down capacitance of 3 pF
■ Onboard thermal shutdown circuitry