UCC5622
27 - Line SCSI Terminator With Split 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
•110Ω Termination
•Completely Meets SCSI Hot Plugging
•–900mA Sourcing Current for Termination
•+500mA Sinking Current for Active Negation
•Logic Command Disconnects all Termination Lines
•Split Disconnect Controls Lines 1 to 9 and 10 to 27 Separately
•Trimmed Impedance to 5%
•Current Limit and Thermal Shutdown Protection
BLOCK DIAGRAM
DESCRIPTION
The UCC5622 provides 27 lines of active termination for a SCSI (Small Computer Systems Interface) parallel bus. The SCSI standard recommends active termination at both ends of the cable.
The UCC5622 is ideal for high performance 5V SCSI systems. During disconnect the supply current is typically only 100µA, which makes the IC attractive for lower powered systems.
The UCC5622 features a split disconnect allowing the user to control termination lines 10 to 27 with disconnect one, DISCNCT1, and control terminiation lines 1 to 9 with disconnect two, DISCNCT2.
The UCC5622 is designed with a low channel capacitance of 2.5pF, which eliminates effects on signal integrity from disconnected terminators at interim points on the bus.
The power amplifier output stage allows the UCC5622 to source full termination current and sink active negation current when all termination lines are actively negated.
The UCC5622, 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 FAST20 SCSI operation.
(continued)
Circuit Design Patented |
UDG-96113 |
|
|
10/98 |
|
ABSOLUTE MAXIMUM RATINGS
TRMPWR Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7V Signal Line Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to +7V Regulator Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5A Storage Temperature . . . . . . . . . . . . . . . . . . . 65°C to +150°C Junction Temperature . . . . . . . . . . . . . . . . . . . 55°C to +150°C Lead Temperature (Soldering, 10 Sec.). . . . . . . . . . . . . +300°C
Currents are positive into, negative out of the specified terminal. Consult Packaging Section of Databook for thermal limitations and considerations of packages.
LQFP-48 (Top View) |
MWP Package |
UCC5622
CONNECTION DIAGRAM
SSOP-44 (Top View)
MWP Package
DESCRIPTION (cont.)
Other features include thermal shutdown and current limit. This device is offered in low thermal resistance versions of the industry standard 44 pin wide body QSOP (MWP) and 48 pin LQFP (FQP). Consult QSOP-44 and LQFP-48 Packaging Diagram for exact dimensions.
ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for TA = 0°C to 70°C, TRMPWR = 4.75V, DISCNCT1 = DSCNCT2 = 0V, TA = TJ.
PARAMETER |
TEST CONDITIONS |
MIN |
TYP |
MAX |
UNITS |
Supply Current Section |
|
|
|
|
|
TRMPWR Supply Current |
All Termination Lines = Open |
|
1 |
2 |
mA |
|
All Termination Lines = 0.2V |
|
630 |
650 |
mA |
Power Down Mode |
DISCNCT1 = DSCNCT2 = TRMPWR |
|
100 |
200 |
A |
2
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