The UCC5614 provides 9 lines of active termination for a SCSI (Small
Computer Systems Interface) parallel bus. The SCSI standard recom-
mends active termination at both ends of the cable.
The UCC5614 is ideal for high performance 3.3V SCSI systems. The key
features contributing to such low operating voltage are the 0.1V drop out
regulator and the 2.7V reference. The reduced reference voltage was
necessary to accommodate the lower termination current dictated in the
SCSI-3 specification. During disconnect the supply current is typically
only 0.5
A, which makes the IC attractive for battery powered systems.
The UCC5614 is designed with an ultra low channel capacitance of
1.8pF, which eliminates effects on signal integrity from disconnected ter-
minators at interim points on the bus.
The UCC5614 can be programmed for either a 110 ohm or 2.5k ohm ter-
mination. The 110 ohm termination is used for standard SCSI bus lengths
and the 2.5k ohm termination is typically used in short bus applications.
When driving the TTL compatible DISCNCT pin directly, the 110 ohm ter-
mination is connected when the DISCNCT pin is driven low, and discon-
nected when driven high. When the DISCNCT pin is driven through an
impedance between 80k and 150k, the 2.5k ohm termination is con-
nected when the DISCNCT pin is driven low, and disconnected when
driven high.
UCC5614
9-Line 3-5 Volt Low Capacitance SCSI Active Terminator
FEATURES
DESCRIPTION
BLOCK DIAGRAM
Circuit Design Patented
Complies with SCSI, SCSI-2 and
SCSI-3 Standards
2.7V to 7V Operation
1.8pF Channel Capacitance during
Disconnect
0.5
A Supply Current in Disconnect
Mode
110 Ohm/2.5k Programmable
Termination
Completely Meets SCSI Hot Plugging
-400mA Sourcing Current for
Termination
+400mA Sinking Current for Active
Negation Drivers
Trimmed Termination Current to 4%
Trimmed Impedance to 7%
Current Limit and Thermal Shutdown
Protection
continued
12/94
UDG-94029-1
UCC5614
The power amplifier output stage allows the UCC5614 to
source full termination current and sink active negation
current when all termination lines are actively negated.
The UCC5614 is pin for pin compatible with Unitrode's
other 9 line SCSI terminators, allowing lower capacitance
and lower voltage upgrades to existing systems. The
UCC5614, as with all Unitrode terminators, is completely
hot pluggable and appears as high impedance at the ter-
minating channels with V
TRMPWR
= 0V or open.
Internal circuit trimming is utilized, first to trim the 110
ohm termination impedance to a 7% tolerance, and then
most importantly, to trim the output current to a 4% toler-
ance, as close to the max SCSI-3 spec 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 16 pin narrow body SOIC, 16 pin
ZIP (Zig-Zag In Line package), 24 pin TSSOP and 28 pin
PLCC.
ABSOLUTE MAXIMUM RATINGS
Termpwr Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7V
Signal Line Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to +7V
Regulator Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . 0.6A
Storage Temperature . . . . . . . . . . . . . . . . . . .
-
-
65C to +150C
Operating Temperature . . . . . . . . . . . . . . . . .
-
-
55C to +150C
Lead Temperature (Soldering, 10 Sec.) . . . . . . . . . . . . . +300C
RECOMMENDED OPERATING CONDITIONS
Termpwr Voltage . . . . . . . . . . . . . . . . . . . . . . . . . 2.7V to 5.25V
Signal Line Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to +5V
Disconnect Input Voltage . . . . . . . . . . . . . . . . . . 0V to Termpwr
Description Continued
Unless otherwise specified all voltages are with respect to
Ground. Currents are positive into, negative out of the speci-
fied terminal.
Consult Packaging Section of Unitrode Integrated Circuits dat-
abook for thermal limitations and considerations of packages.
CONNECTION DIAGRAMS
DIL-16 (Top View)
N or J Package
ZIP-16 (Top View)
Z Package
Note: Drawings are not to scale.
2
UCC5614
Note: Drawings are not to scale.
CONNECTION DIAGRAMS (cont.)
* DP package pin 5 serves as signal ground; pins 4, 12, 13
serve as heatsink/ground.
* PWP package pin 5 serves as signal ground; pins 6, 7, 8, 9,
17, 18, 19, and 20 serve as heatsink/ground.
SOIC-16 (Top View)
DP Package
TSSOP-24 (Top View)
PWP Package
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
Supply Current Section
Termpwr Supply Current
All termination lines = Open
1
2
mA
All termination lines = 0.2V
210
218
mA
Power Down Mode
DISCNCT = Termpwr
0.5
5
A
Output Section (110 ohms - Terminator Lines)
Terminator Impedance
102.3
110
117.7
Ohms
Output High Voltage
(Note 1)
2.5
2.7
3.0
V
Max Output Current
V
LINE
= 0.2V T
J
= 25
C
-
-
22.1
-
-
23
-
-
24
mA
V
LINE
= 0.2V
-
-
21
-
-
23
-
-
24
mA
V
LINE
= 0.2V, TRMPWR = 3V T
J
= 25
C (Note 1)
-
-
20.2
-
-
23
-
-
24
mA
V
LINE
= 0.2V, TRMPWR = 3V (Note 1)
-
-
19
-
-
23
-
-
24
mA
V
LINE
= 0.5V
-
-
22.4
mA
Output Leakage
DISCNCT = 2.4V, TRMPWR = 0V to 5.25V
10
400
nA
Output Capacitance
DISCNCT = 2.4V (Note 2) (DP Package)
1.8
2.5
pF
Output Section (2.5k ohms - Terminator Lines) (R
DISCNCT
= 80k ohms)
Terminator Impedance
2
2.5
3
k
Output High Voltage
TRMPWR = 3V (Note 1)
2.5
2.7
3.0
V
Max Output Current
V
LINE
= 0.2V
-
-
0.7
-
-
1
-
-
1.4
mA
V
LINE
= 0.2V, TRMPWR = 3V (Note 1)
-
-
0.6
-
-
1
-
-
1.5
mA
Output Leakage
DISCNCT = 2.4V, TRMPWR = 0 to 5.25V
10
400
nA
Output Capacitance
DISCNCT = 2.4V (Note 2) (DP Package)
1.8
2.5
pF
Regulator Section
Regulator Output Voltage
5.25V > TRMPWR > 3V
2.5
2.7
3.0
V
Drop Out Voltage
All Termination Lines = 0.2V
0.1
0.2
V
Short Circuit Current
V
REG
= 0V
-
-
200
-
-
400
-
-
800
mA
ELECTRICAL CHARACTERISTICS
Unless otherwise stated, these specifications apply for T
A
= 0C to 70C.
TRMPWR = 3.3V, DISCNCT = 0V, R
DISCNCT
= 0 ohms. T
A
= T
J
.
3
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
Regulator Section (cont.)
Sinking Current Capability
V
REG
= 3V
200
400
800
mA
Thermal Shutdown
(Note 2)
170
C
Thermal Shutdown Hysteresis
(Note 2)
10
C
Disconnect Section
Disconnect Threshold
R
DISCNCT
= 0 & 80k
0.8
1.5
2.0
V
Input Current
DISCNCT = 0V
30
50
A
ELECTRICAL CHARACTERISTICS (cont.)
Unless otherwise stated, these specifications apply for T
A
= 0C to 70C.
TRMPWR = 3.3V, DISCNCT = 0V, R
DISCNCT
= 0 ohms. T
A
= T
J
.
UCC5614
Note 1: Measuring each termination line while other 8 are low (0.2V).
Note 2: Guaranteed by design. Not 100% tested in production.
Figure 1: Typical SCSI Bus Configurations Utilizing 2 UCC5614 Devices
Figure 2: Typical Wide SCSI Bus Configurations Utilizing 3 UCC5614 Devices.
APPLICATION INFORMATION
UNITRODE INTEGRATED CIRCUITS
7 CONTINENTAL BLVD.
MERRIMACK, NH 03054
TEL. (603) 424-2410
FAX (603) 424-3460
4
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