UCC5622
DESCRIPTION
The UCC5622 provides 27 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 UCC5622 is ideal for high performance 5V SCSI systems. During dis-
connect the supply current is typically only 100 A, which makes the IC at-
tractive for lower powered systems.
The UCC5622 features a split disconnect allowing the user to control termi-
nation lines 10 to 27 with disconnect one, DISCNCT1, and control terminia-
tion 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 in-
terim points on the bus.
The power amplifier output stage allows the UCC5622 to source full termi-
nation current and sink active negation current when all termination lines
are actively negated.
The UCC5622, 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-
20 SCSI operation.
(continued)
27 - Line SCSI Terminator With Split Disconnect
BLOCK DIAGRAM
FEATURES
Complies with SCSI, SCSI-2, SCSI-3,
SPI and FAST-20 (Ultra) Standards
2.5pF Channel Capacitance During
Disconnect
100 A 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
Split Disconnect Controls Lines 1 to 9
and 10 to 27 Separately
Trimmed Impedance to 5%
Current Limit and Thermal Shutdown
Protection
SLUS291A - OCTOBER 1999 - REVISED 2002
UDG-96113
Circuit Design Patented
2
UCC5622
Other features include thermal shutdown and current
limit. This device is offered in low thermal resistance ver-
sions of the industry standard 44 pin wide body QSOP
(MWP). Consult QSOP-44 Packaging Diagram for exact
dimensions.
DESCRIPTION (cont.)
L9
L8
L23
L24
1
2
3
4
N/C
N/C
L25
L26
5
6
7
8
GND
L27
GND
GND
9
10
11
12
DISCNCT1
GND
DISCNCT2
L10
13
14
15
16
L12
L11
L13
L14
17
18
19
20
L2
L1 21
22
L8
L7
L5
L22
44
43
42
41
L21
N/C
L20
L19
40
39
38
37
GND
REG
GND
GND
36
35
34
33
TRMPWR
GND
L18
L17
32
31
30
29
N/C
L16
N/C
L15
28
27
26
25
L3
L4
24
23
CONNECTION DIAGRAM
QSOP-44 (Top View)
MWP Package
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 termi-
nal. Consult Packaging Section of Databook for thermal limita-
tions and considerations of packages.
ELECTRICAL CHARACTERISTICS
Unless otherwise stated, these specifications apply for T
A
= 0C to 70C,
TRMPWR = 4.75V, DISCNCT1 = DSCNCT2 = 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
DISCNCT1 = DSCNCT2 = 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
= 25 C
22.1
23.3
24
mA
V
LINE
= 0.2V
20.7
23.3
24
mA
V
LINE
= 0.2V, TRMPWR = 4V, T
J
= 25 C (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
DISCNCT1 = DISCNCT2 = 2.4V, TRMPWR = 0V to
5.25V
10
400
nA
Output Capacitance
DISCNCT1 = DISCNCT2 = 2.4V (Note 2)
2.5
4
pF
3
UCC5622
ELECTRICAL CHARACTERISTICS
Unless otherwise stated, these specifications apply for T
A
= 0C to 70C,
TRMPWR = 4.75V, DISCNCT1 = DSCNCT2 = 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 DISCNCT1
Controls Lines 10 to 27
0.8
1.5
2.0
V
Input Current DISCNCT1
DISCNCT1 = 0V
10
30
A
Disconnect Threshold DISCNCT2
Controls Lines 1 to 9
0.8
1.5
2
V
Input Current DISCNCT2
DISCNCT2 = 0V
10
30
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
2 0
PIN DESCRIPTIONS
DISCNCT1: Disconnect one controls termination lines
10 27. Taking this pin high or leaving it open causes
termination lines 10 - 27 to become high impedance, tak-
ing this pin low allows the channels to provide normal ter-
mination.
DISCNCT2: Disconnect two controls termination lines
1 9. Taking this pin high or leaving it open causes
termination lines 1 - 9 to become high impedance. Taking
this pin low allows the channels to provide normal
termination. Taking both disconnect pins high or leaving
them open will put the chip in to sleep mode where it will
be in low-power mode.
GND: Ground reference for the IC.
L1 L27: 110
termination channels.
REG: Output of the internal 2.7V regulator.
TRMPWR: Power for the IC.
TRMPWR
REG
TO SCSI BUS
TRMPWR
DISCNCT1
DATA BYTE 1
AND CONTROL BITS
L27
L10
4.7
F
4.7
F
DISCNCT2
TO DRIVERS
AND RECEIVERS
UC5622
DATA BYTE 2
L9
L1
DISCNCT1 CONTROLS BITS 10 THRU 27
DISCNCT2 CONTROLS BITS 1 THRU 9
Figure 1. Typical Wide SCSI Bus Configuration Using the UCC5622
UDG-98172
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