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SLUS195B − MARCH 1997 − REVISED NOVEMBER 2003
D
D
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Complies with SCSI, SCSI−2 and SPI−2
Standards
D
Logic Command Disconnects all
Termination Lines
6-pF Channel Capacitance during
Disconnect
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D
Trimmed Termination Current to 3%
Trimmed Impedance to 3%
100-µA Supply Current in Disconnect Mode
Meets SCSI Hot Plugging
Negative Clamping on all Signal Lines
Current Limit and Thermal Shutdown
Protection
−400-mA Sourcing Current for Termination
+400-mA Sinking Current for Active
Negation Drivers
description
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 6 pF 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 5 V, while the regulator remains at its nominal value, reduced channel capacitance to 6 pF
typical, and as with the UC5601, custom power packages are utilized to allow normal operation at full power
conditions (1.2 watts).
functional block diagram
UDG-94049
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
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Copyright 2003, Texas Instruments Incorporated
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