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Current Limit and Thermal Shutdown
Protection
DESCRIPTION
UCC5619 provides 27 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.
The UCC5619 is ideal for high performance 5V SCSI systems. During dis-
connect the supply current is typically only 100碌A(chǔ), which makes the IC at-
tractive for lower powered systems.
The UCC5619 is designed with a low channel capacitance of 2.5pF, which
eliminates effects on signal integrity from disconnected terminators at in-
terim points on the bus.
The power amplifier output stage allows the UCC5619 to source full termi-
nation current and sink active negation current when all termination lines
are actively negated.
The UCC5619, as with all Unitrode terminators, is completely hot pluggable
and appears as high impedance at the teminating channels with V
TRMPWR
= 0V or open.
Internal circuit trimming is utilized, first to trim the 110鈩?impedance, and
then most importantly, to trim the output current as close to the maximum
SCSI-3 specification 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 36 pin
wide body QSSOP (MWP) and 48 pin LQFP (FQP).
Consult SSOP-36 (MWP QSSOP-36) and FQP-48 Packaging Diagram for
exact dimensions.
BLOCK DIAGRAM
Circuit Design Patented
UDG-96108
10/98
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