SCSI Termination 3.3V/5V 16-Pin SOIC T/R

The UCC5614 provides 9 lines of active termination for a small computer systems interface (SCSI) parallel bus. The SCSI standard recommends active termination at both ends of the cable segment. The UCC5614 is ideal for high performance 3.3-V SCSI systems. The key features contributing to such low operating voltage are the 0.1-V drop-out regulator and the 2.7-V reference. During disconnect the supply current is typically only 0.5 µA, which makes the device attractive for battery powered systems. The UCC5614 is designed with an ultra low channel capacitance of 1.8 pF, which eliminates effects on signal i cted terminators at interim points on the bus. The UCC5614 can be programmed for either a 110-O termination is used for standard SCSI bus lengths and the 2.5-kO termination is typically used in short bus applications. When driving the TTL compatible DISCNCT pin directly, the 110-O termination is connected when the DISCNCT pin is driven low, and disconnected when driven high. When the DISCNCT pin is driven through an impedance between 80 kO termination is connected when the DISCNCT pin is driven low and disconnected when driven high. The power amplifier output stage allows the UCC5614 to source full termination current and sink active negation current when all termination lines are actively negated. The UCC5614 is pin for pin compatible with Unitrodes other 9-line SCSI terminators, allowing lower capacitance and lower voltage upgrades to existing systems. The UCC5614, as with all Unitrode terminators, is completely hot pluggable and appears as high impedance at the terminating channels with VTRMPWR = 0 V or open. Internal circuit trimming is utilized, first to trim the 110-O termination impedance to a 7% tolerance, and then most importantly, to trim the output current to a 4% tolerance, as close to the max SCSI specification as possible, which maximizes noise margin in fast SCSI operation. Other features include thermal shutdown and current limit. This device is offered in low thermal resistance versions of the industry standard 16-pin narrow body SOIC, 16-pin N and 24-pin TSSOP.

Complies with SCSI, SCSI-2 and SPI-2 Single Ended Standards

2.7-V to 5.25-V Operation

1.8-pF Channel Capacitance during Disconnect

0.5-µA Supply Current in Disconnect Mode

110 O Programmable Termination

Completely Meets SCSI Hot Plugging

400-mA Sourcing Current for Termination

+400-mA Sinking Current for Active Negation Drivers

Trimmed Termination Current to 4%

Trimmed Impedance to 7%

Current Limit and Thermal Shutdown Protection