UC5603

The UC5603 provides 9 lines of active termination for a SCSI (Small Computers Systems Interface) parallel bus. The SCSI standard recommends active termination at both ends of the cable segment.

The UC5603 provides a disconnect feature which, when opened or driven high, will disconnect all terminating resistors, and disables the regulator; greatly reducing standby power. The output channels remain high impedance even without Termpwr applied. A low channel capacitance of 6pF allows units at interim points of the bus to have little to no effect on the signal integrity.

Functionally the UC5603 is similar to its predecessor, the UC5601 - 18 line Active Terminator. Several electrical enhancements were incorporated in the UC5603, such as a sink/source regulator output stage to accommodate all signal lines at +5V, while the regulator remains at its nominal value, reduced channel capacitance to 6pF typical, and as with the UC5601, custom power packages are utilized to allow normal operation at full power conditions (1.2 watts).

Internal circuit trimming of UC5603 is utilized, first to trim the impedance to a 3% tolerance, and then most importantly, to trim the output current to a 3% tolerance, as close to the max SCSI spec as possible, which maximizes noise margin in fast SCSI operation.

Other features of UC5603 include negative clamping on all signal lines to protect external circuitry from latch-up, thermal shutdown and current limit. 

This UC5603 is offered in low thermal resistance versions of the industry standard 16 pin narrow body SOIC, 16 pin ZIP (zig-zag in line package) and 24 pin TSSOP.