DS21S07A

SCSI Terminator

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Overview

Fully compliant with SCSI-1, Fast, and Ultra SCSI standards
Backward-compatible with DS2107 and DS2107A
Provides active signal termination for 9 lines
Handles actively negated SCSI signals
Laser-trimmed 110-ohm resistors with 2% tolerance
Low drop-out voltage of 3pF
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

The DS21S07A is backward-compatible replacement for the DS2107A providing precision resistance values for SCSI-1, Fast, and Ultra SCSI with 2% tolerance.

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.

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.