UCC5619_09 Datasheet, PDF (1/7 Pages) Texas Instruments – 27-Line SCSI Terminator With Reverse Disconnect

UCC5619
27-Line SCSI Terminator With Reverse Disconnect
FEATURES
• Complies with SCSI, SCSI-2, SCSI-3,
SPI and FAST-20 (Ultra) Standards
• 2.5pF Channel Capacitance during
Disconnect
• 100µA Supply Current in Disconnect
Mode
• 4V To 7V Operation
• 110 Termination
• Completely Meets SCSI Hot Plugging
• –900mA Sourcing Current for
Termination
• +500mA Sinking Current for Active
Negation
• Logic Command Disconnects all
Termination Lines
• Trimmed Impedance to 5%
• Current Limit and Thermal Shutdown
Protection
BLOCK DIAGRAM
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 100µA, 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 VTRMPWR
= 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 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).
Consult SSOP-36 (MWP QSSOP-36) Packaging Diagram for exact dimen-
sions.
Circuit Design Patented
SLUS265A - OCTOBER 1998 - REVISED - APRIL 2002
UDG-96108