UC5608
18-Line Low Capacitance SCSI Active Terminator
FEATURES
DESCRIPTION
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Complies with SCSI, SCSI-2 and SPI-2
Standards
The UC5608 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.
6pF Channel Capacitance during
Disconnect
The UC5608 is pin-for-pin compatible with its predecessors, the
UC5601 and UC5602 - 18 Line Active Terminator. Parametrically the
UC5608 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).
100µA Supply Current in Disconnect
Mode
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Meets SCSI Hot Plugging Capability
−650mA Sourcing Current for
Termination
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.
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+200mA Sinking Current for Active
Negation
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Provides Active Termination for 18 Lines
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.
Logic Command Disconnects all
Termination Lines
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Trimmed Termination Current to 5%
Trimmed Impedance to 5%
Other features include 4.0 to 5.25V Termpwr, thermal shutdown and
current limit.
Current Limit and Thermal Shutdown
Protection
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-94047
Circuit Design Patented
3/97
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