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Reverse Disconnect
Complies with SCSI, SCSI-2 and SPI-2
Standards
6pF Channel Capacitance during
Disconnect
100碌A(chǔ) Supply Current in Disconnect
Mode
Meets SCSI Hot Plugging Capability
鈭?50mA
Sourcing Current for
Termination
+200mA Sinking Current for Active
Negation
Provides Active Termination for 18 Lines
Logic Command Disconnects all
Termination Lines
Trimmed Termination Current to 5%
Trimmed Impedance to 5%
Current Limit and Thermal Shutdown
Protection
DESCRIPTION
The UC5609 provides 18 lines of active termination for a SCSI (Small
Computer Systems Interface) parallel bus. The SCSI standard recom-
mends active termination at both ends of the bus cable.
The UC5609 is pin-for-pin compatible with its predecessors, the
UC5601, UC5602 and UC5608 - 18 Line Active Terminators, except
for the reverse disconnect sense. Parametrically the UC5609 has a
5% tolerance on impedance and current compared to a 3% tolerance
on the UC5601 and the sink current is increased from 20 to 200mA.
The low side clamps have been removed. Custom power packages
are utilized to allow normal operation at full power conditions (2
Watts).
When in disconnect mode the terminator will disconnect all terminat-
ing resistors and disable the regulator, greatly reducing standby
power. The output channels remain high impedance even without
Termpwr applied.
Internal circuit trimming is utilized to trim the impedance to a 5% toler-
ance and, most importantly, to trim the output current to a 5% toler-
ance, as close to the max SCSI spec as possible, which maximizes
noise margin in fast SCSI operation.
Other features include 4.0 to 5.25V Termpwr, thermal shutdown and
current limit.
This device is offered in low thermal resistance versions of the indus-
try standard 28 pin wide body SOIC, 28 pin wide body TSSOP, and 28
pin PLCC, as well as 24 pin DIP.
BLOCK DIAGRAM
UDG-94126
Circuit Design Patented
4/97
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