SCSI Termination 5V 44-Pin SSOP T/R

The UCC5622 provides 27 lines of active termination for a SCSI (Small Computer Systems Interface) parallel bus. The SCSI standard recommends active termination at both ends of the cable. The UCC5622 is ideal for high performance 5V SCSI systems. During disconnect the supply current is typically only 100uA, which makes the IC attractive for lower powered systems. The UCC5622 features a split disconnect allowing the user to control termination lines 10 to 27 with disconnect one, DISCNCT1, and control terminiation lines 1 to 9 with disconnect two, DISCNCT2. The UCC5622 is designed with a low channel capacitance of 2.5pF, which eliminates effects on signal integrity from disconnected terminators at interim points on the bus. The power amplifier output stage allows the UCC5622 to source full termination current and sink active negation current when all termination lines are actively negated. The UCC5622, as with all Unitrode terminators, is completely hot pluggable and appears as high impedance at the teminating channels with VTRMPWR = 0V or open. Internal circuit trimming is utilized, first to trim the 110O impedance, and then most importantly, to trim the output current as close to the maximum SCSI-3 specification as possible, which maximizes noise margin in FAST-20 SCSI operation. Other features include thermal shutdown and current limit. This device is offered in low thermal resistance versions of the industry standard 44 pin wide body QSOP (MWP). Consult QSOP-44 Packaging Diagram for exact dimensions.

Complies with SCSI, SCSI-2, SCSI-3, SPI and FAST-20 (Ultra) Standards

2.5pF Channel Capacitance During Disconnect

100uA Supply Current in Disconnect Mode

4V To 7V Operation

110O Termination

Completely Meets SCSI Hot Plugging

–900mA Sourcing Current for Termination

+500mA Sinking Current for Active Negation

Logic Command Disconnects all Termination Lines

Split Disconnect Controls Lines 1 to 9 and 10 to 27 Separately

Trimmed Impedance to 5%

Current Limit and Thermal Shutdown Protection