SCSI Terminator

The DS21T05 is functionally compatible with the DS21T07 providing resistance values for SCSI-1, Fast, and Ultra SCSI but with relaxed output current and termination tolerances.

Each chip actively terminates cable segments in SCSI systems carrying nine single-ended drivers and receivers. In an 8-bit wide SCSI arrangement, two DS21S07As connected at each end of the SCSI cable can terminate 18 active signal lines. A 16-bit wide SCSI arrangement requires three DS21S07As at each end to terminate 27 active signal lines.

SCSI termination is used wherever data must be transmitted without voltage drops caused by signal reflection at the parallel bus termination point, which is often significant in multidropped systems.

The DS21T05 is suitable for high-volume applications that require active termination but not the high performance of the DS21T07.

All Dallas terminators feature power-down mode with extremely low-quiescent consumption. Different SCSI terminators are available to match every existing SCSI protocol and to address different design concerns, such as price, board space, and voltage differential.

* Fully compliant with SCSI-1, Fast, and Ultra SCSI standards

* Backward-compatible with DS2105

* Provides active signal termination for 9 lines

* Handles actively negated SCSI signals

* Laser-trimmed 110-ohm resistors with 5% tolerance

* Low drop-out voltage of 3pF

* Low standby current consumption of 100µA

* Power-down mode with resistors isolated from bus

* SCSI bus hot-plug compatible

* Onboard thermal shutdown circuitry

* Operating range:

* 0°C to +70°C

* 4.0V to 5.5V