UCC5620
DESCRIPTION
UCC5620 provides 27 lines of active termination for a SCSI (Small Com-
puter Systems Interface) parallel bus. The SCSI standard recommends
active termination at both ends of the cable.
The UCC5620 is ideal for high performance 5V SCSI systems. During
disconnect the supply current is typically only 100
A, which makes the IC
attractive for lower powered systems.
The UCC5620 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 UCC5620 to source full ter-
mination current and sink active negation current when all termination
lines are actively negated.
The UCC5620, as with all Unitrode terminators, is completely hot plugga-
ble and appears as high impedance at the teminating channels with
V
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.
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 QSOP (MWP).
Consult QSOP-36 packaging diagram for exact dimensions.
27-Line SCSI Terminator
BLOCK DIAGRAM
FEATURES
Complies with SCSI, SCSI-2, SCSI-3,
SPI and FAST-20 (Ultra) Standards
2.5pF Channel Capacitance during
Disconnect
100mA 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
SLUS287B - OCTOBER 1999 - REVISED APRIL 2002
UDG-96109
Circuit Design Patented
2
UCC5620
Termpwr 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 termi-
nal. Consult Packaging Section of Databook for thermal limita-
tions and considerations of packages.
ABSOLUTE MAXIMUM RATINGS
DISCNCT
GND
LINE21
LINE20
LINE19
LINE7
LINE23
LINE9
GND
LINE27
GND
LINE24
LINE25
LINE26
LINE8
GND
LINE10
REG
GND
GND
LINE11
LINE12
14
13
12
11
10
9
8
7
6
5
4
3
2
1
23
24
25
26
27
28
29
30
31
32
33
34
35
36
18
17
16
15
LINE15
LINE3
LINE4
19
20
21
22
LINE13
LINE14
LINE1
LINE2
TRMPWR
LINE18
LINE17
LINE16
LINE22
LINE5
LINE6
CONNECTION DIAGRAM
SSOP-36 (Top View)
MWP Package
ELECTRICAL CHARACTERISTICS
Unless otherwise stated, these specifications apply for T
A
= 0C to 70C, TRMPWR
= 4.75V, DISCNCT = 0V, T
A
= T
J
.
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
DISCNCT = TRMPWR
100
200
A
Output Section (Termination Lines)
Termination Impedance
(Note 3)
104.5
110
115.5
Output High Voltage
(Note 1)
2.6
2.8
3.0
V
Max Output Current
V
LINE
= 0.2V, T
J
= 25C
-22.1 -23.3
-24
mA
V
LINE
= 0.2V
-20.7 -23.3
-24
mA
V
LINE
= 0.2V, TRMPWR = 4V, T
J
= 25C (Note 1)
-21
-23
-24
mA
V
LINE
= 0.2V, TRMPWR = 4V (Note 1)
-20
-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)
2.5
4
pF
3
UCC5620
ELECTRICAL CHARACTERISTICS
Unless otherwise stated, these specifications apply for T
A
= 0C to 70C, TRMPWR
= 4.75V, DISCNCT = 0V, T
A
= T
J
.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
Regulator Section
Regulator Output Voltage
2.6
2.8
3.0
V
Drop Out Voltage
All Termination Lines = 0.2V
0.4
0.8
V
Short Circuit Current
V
REG
= 0V
-650
-900 1300
mA
Sinking Current Capability
V
REG
= 3.5V
300
500
900
mA
Thermal Shutdown
170
C
Thermal Shutdown Hysteresis
10
C
Disconnect Section
Disconnect Threshold
0.8
1.5
2.0
V
Input Current
DISCNCT = 0V
20
60
A
Note 1: Measuring each termination line while other 26 are low (0.2V).
Note 2: Ensured by design. Not 100% tested in production.
Note 3: Tested by measuring I
OUT
with V
OUT
= 0.2V and V
OUT
with no load, then calculate:
(
)
Z
V
N L
V
I
at
V
OUT
OUT
=
-
. .
.
.
0 2
0 2
PIN DESCRIPTIONS
DISCNCT: Taking this pin high or leaving it open causes
all channels to become high impedance, and the chip to
go into low-power mode; a low state allows the channels
to provide normal termination.
GND: Ground reference for the IC.
LINE1 - LINE27: 110
termination channels.
REG: Output of the internal 2.7V regulator.
TRMPWR: Power for the IC.
TRMPWR
REG
TO SCSI BUS
TRMPWR
DATA BYTES 1 AND 2
+2 PARITY BITS
L1
4.7
F
4.7
F
DISCNCT
TO DRIVERS
AND RECEIVERS
UCC5620
CONTROL BITS
L27
Figure 1. Typical Wide SCSI Bus Configuration Using the UCC5620
APPLICATION INFORMATION
UDG-98188
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