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Complies with SCSI, SCSI-2
Standards
9pF Channel Capacitance during
Disconnect
100碌A(chǔ) Supply Current in
Disconnect Mode
Meets SCSI Hot Plugging Capability
鈭?00mA
Sourcing Current for
Termination
+40mA Sinking Current for Active
Negation
Logic Command Disconnects all
Termination Lines
Trimmed Termination Current to 7%
Trimmed Impedance to 7%
Current Limit and Thermal
Shutdown Protection
DESCRIPTION
The UC5604 provides 9 lines of active termination for a SCSI (Small Com-
puter Systems Interface) parallel bus. The SCSI standard recommends ac-
tive termination at both ends of the cable segment.
The UC5604 provides a disconnect feature which, when opened or driven
high, will disconnect all terminating resistors and disable the regulator,
greatly reducing standby power. The output channels remain high imped-
ance even without Termpwr applied.
The UC5604 is pin-for-pin compatible with its predecessor, the UC5603 - 9
line Active Terminator. The only functional difference between the UC5604
and UC5603 is the absence of the negative clamps. Parametrically, the
UC5604 has a 7% tolerance on impedance and current compared to a 3%
tolerance on the UC5603 and the sink current is reduced from 300mA to
40mA. Custom power packages are utilized to allow normal operation at
full power conditions (1.2 watts).
Internal circuit trimming is utilized, first to trim the impedance to a 7% toler-
ance, and then most importantly, to trim the output current to a 7% toler-
ance, as close to the max SCSI spec 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 ZIP (zig-zag in line package)
and 24 pin TSSOP.
BLOCK DIAGRAM
UDG-94064
Circuit Design Patented
3/97
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