TI UCC5618N

The UCC5618 provides 18 lines of active termination for a SCSI (Small Computers Systems Interface) parallel bus. The SCSI standard recommends and Fast-20 (Ultra) requires active termination at both ends of the cable. Pin for pin compatible with the UC5601 and UC5608, the UCC5618 is ideal for high performance 5V SCSI systems, Termpwr 4.0 - 5.25V. During disconnect the supply current is only 50μA typical, which makes the IC attractive for lower powered systems. The UCC5618 is designed with a low channel capacitance of 2pF, which eliminates effects on signal integrity from disconnected terminators at interim points on the bus. The power amplifier output stage allows the UCC5618 to source full termination current and sink active negation current when all termination lines are actively negated. The UCC5618, as with all Unitrode terminators, is completely hot pluggable and appears as high impedance at the terminating channels with TRMPWR {=0V or open. Internal circuit trimming is utilized, first to trim the 110Ω impedance, and then most importantly, to trim the output current as close to the max SCSI - 3 spec as possible, which maximizes noise margin in fast SCSI operation. This device is offered in low thermal resistance versions of the industry standard 28 pin wide body SOIC, TSSOP and PLCC.

• Complies with SCSI, SCSI - 2, SCSI - 3, SPI and FAST - 20 Standards
• 2pF Channel Capacitance During Disconnect
• 50μA Supply Current in Disconnect Mode
• 110Ω Termination
• SCSI Hot Plugging Compliant, 10nA Typical
• +400mA Sinking Current for Active Negation
• -650mA Sourcing Current for Termination
• Trimmed Impedance to 5%
• Thermal Shutdown
• Current Limit