UCC5618
18-Line SCSI Terminator
FEATURES
DESCRIPTION
• Complies with SCSI, SCSI-2, SCSI-3, The UCC5618 provides 18 lines of active termination for a SCSI (Small
SPI and FAST-20 Standards
Computers Systems Interface) parallel bus. The SCSI standard recom-
mends and Fast-20 (Ultra) requires active termination at both ends of the
cable.
• 2pF Channel Capacitance During
Disconnect
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.
• 50µA Supply Current in Disconnect
Mode
• 110Ω Termination
• SCSI Hot Plugging Compliant, 10nA
Typical
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.
• +400mA Sinking Current for Active
Negation
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.
• –650mA Sourcing Current for
Termination
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.
• Trimmed Impedance to 5%
• Thermal Shutdown
• Current Limit
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
UDG-96005-1
Patented Circuit Design
6/98