UCC5617_15 Datasheet, PDF (1/8 Pages) Texas Instruments – 18-Line SCSI Terminator (Reverse Disconnect)

UCC5617
18-Line SCSI Terminator (Reverse Disconnect)
FEATURES
• Complies with SCSI, SCSI-2, SCSI-3,
SPI and FAST-20 Standards
• 2pF Channel Capacitance During
Disconnect
• 50mA Supply Current in Disconnect
Mode
• 110 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
BLOCK DIAGRAM
DESCRIPTION
The UCC5617 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 UC5609, the UCC5617 is ideal for high per-
formance 5V SCSI systems, Termpwr 4.0-5.25V. During disconnect the
supply current is only 50 A typical, which makes the IC attractive for lower
powered systems.
The UCC5617 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 UCC5617 to source full termi-
nation current and sink active negation current when all termination lines
are actively negated.
The UCC5617, 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 110 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.
This device is offered in low thermal resistance versions of the industry
standard 28 pin wide body SOIC.
Patented Circuit Design
SLUS351A - APRIL 1997 - REVISED AUGUST 2002
UDG-96073