GENERAL DESCRIPTION Fast SCSI and Ultra SCSI require the use of active terminations at both ends of every cable segment in a SCSI system with single-ended drivers and receivers. The DS21S07A SCSI terminator, which is fully compliant with these standards, enables the designer to gain the benefits of active termination: greater immunity to voltage drops on the TERMPWR (TERMination PoWeR) line, enhanced high-level noise immunity, intrinsic TERMPWR decoupling, and very low quiescent current consumption. The DS21S07A integrates a regulator and nine precise switched 110Ω termination resistors into a monolithic IC. The DS21S07A can be electrically isolated from the SCSI bus without physical removal from the SCSI device. FEATURES ■ Fully Compliant with SCSI-1, Fast SCSI, and Ultra SCSI ■ Backward Compatible to the DS2107 and DS2107A ■ Provides Active Termination for Nine Signal Lines ■ Laser-Trimmed 110Ω Termination Resistors Have 2% Tolerance ■ Low Drop-Out Voltage Regulator ■ Power-Down Mode Isolates Termination Resistors from the Bus ■ SCSI Bus Hot Plug Compatible ■ Fully Supports Actively Negated SCSI Signals ■ On-Board Thermal Shutdown Circuitry ■ 16-Pin Plastic SO (DS21S07AS) and 20-Pin Plastic TSSOP (Thin Shrink Small Outline Package) (DS21S07AE)
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