鈥?/div>
Complies with SCSI, SCSI-2 and
SPI-2 Standards
3pF Channel Capacitance during
Disconnect
100碌A(chǔ) Supply Current in
Disconnect Mode
Meets SCSI Hot Plugging Capability
鈭?00mA
Sourcing Current for
Termination
+400mA Sinking Current for Active
Negation
Logic Command Disconnects all
Termination Lines
Trimmed Termination Current to 5%
Trimmed Impedance to 5%
Current Limit and Thermal
Shutdown Protection
DESCRIPTION
The UC5613 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 UC5613 provides a disconnect feature which, when opened or driven
high, disconnects all terminating resistors and disables the regulator
greatly reducing standby power. The output channels remain high imped-
ance even without Termpwr applied. A low channel capacitance of 3pF al-
lows units at interim points of the bus to have little or no effect on the signal
integrity.
The UC5613 is pin-for-pin compatible with its predecessor, the UC5603 - 9
line Active Terminator. The only functional difference between the UC5613
and UC5603 is the absence of the negative clamps. Parametrically, the
UC5613 has a 5% tolerance on impedance and current compared to a 3%
tolerance on the UC5603. Custom power packages are utilized to allow
normal operation at full power (1.2 watts).
Internal circuit trimming is utilized, first to trim the impedance to a 5% toler-
ance; then, the output current is trimmed to a 5% tolerance. The output
current trim is set as close as possible to the maximum value of the SCSI
specification which maximizes the noise margin for 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-94003-1
3/97
Powered by ICminer.com Electronic-Library Service CopyRight 2003
Circuit Design Patented
1
2
3
4
5
