UCC5618
18-Line SCSI Terminator
FEATURES
•
Complies with SCSI, SCSI-2, SCSI-3,
SPI and FAST-20 Standards
•
2pF Channel Capacitance During
Disconnect
•
50µA Supply Current in Disconnect
Mode
•
110Ω Termination
•
SCSI Hot Plugging Compliant, 10nA
Typical
•
+400mA Sinking Current for Active
Negation
•
–650mA Sourcing Current for
Termination
•
Trimmed Impedance to 5%
•
Thermal Shutdown
•
Current Limit
DESCRIPTION
The UCC5618 provides 18 lines of active termination for a SCSI (Small
Computers Systems Interface) parallel bus. The SCSI standard recom-
mends and Fast-20 (Ultra) requires active termination at both ends of the
cable.
Pin for pin compatible with the UC5601 and UC5608, the UCC5618 is ideal
for high performance 5V SCSI systems, Termpwr 4.0-5.25V. During discon-
nect the supply current is only 50µA typical, which makes the IC attractive
for lower powered systems.
The UCC5618 is designed with a low channel capacitance of 2pF, which
eliminates effects on signal integrity from disconnected terminators at in-
terim points on the bus.
The power amplifier output stage allows the UCC5618 to source full termi-
nation current and sink active negation current when all termination lines
are actively negated.
The UCC5618, as with all Unitrode terminators, is completely hot pluggable
and appears as high impedance at the terminating channels with
TRMPWR=0V or open.
Internal circuit trimming is utilized, first to trim the 110Ω impedance, and
then most importantly, to trim the output current as close to the max
SCSI-3 spec as possible, which maximizes noise margin in fast SCSI op-
eration.
This device is offered in low thermal resistance versions of the industry
standard 28 pin wide body SOIC, TSSOP and PLCC.
BLOCK DIAGRAM
Patented Circuit Design
UDG-96005-1
6/98
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