ETC UC5602QP

UC5602
SCSI Active Terminator
FEATURES
DESCRIPTION
•
Complies with SCSI, SCSI-2
Standards
•
10pF Channel Capacitance During
Disconnect
•
The UC5602 is a pin compatible version of its predecessor, the UC5601,
and is targeted for high volume applications which require active termination, but not the high performance of the UC5601. The major differences
are relaxed output current and termination tolerances, and the absence of
low side clamps.
Active Termination for 18 Lines
•
Logic Command Disconnects all
Termination Lines
•
Low Supply Current in Disconnect
Mode
•
Trimmed Regulator for Accurate
Termination Current
•
Current Limit and Thermal
Shutdown Protection
•
110 Ohm Termination
•
Meets SCSI Hot Plugging
The UC5602 provides 18 lines of active termination for a SCSI (Small
Computer Systems Interface) parallel bus. The SCSI-2 standard recommends active termination at both ends of the cable segment, and SCSI-3
will make it a requirement.
The UC5602 provides a disconnect feature which, when opened or driven
high, will disconnect all terminating resistors, and disables the regulator;
greatly reducing standby power. The output channels remain high impedance even without Termpwr applied.
Internal circuit trimming is utilized, first to trim the impedance to a 7% tolerance; and then most importantly, to trim the output current 7% tolerance,
as close to the max SCSI as possible, which maximizes noise margin in
fast SCSI operation.
Other features include thermal shutdown, current limit, and 40mA of active
negation sink current capability.
This device is offered in low thermal resistance versions of the industry
standard 28 pin wide body SOIC and PLCC, as well as a 24 pin DIL plastic
package.
BLOCK DIAGRAM
UDG-94052
10/94
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Circuit Design Patented
UC5602
ABSOLUTE MAXIMUM RATINGS
CONNECTION DIAGRAMS
Termpwr Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7V
Signal Line Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to +7V
Regulator Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5A
Storage Temperature . . . . . . . . . . . . . . . . . . . −65°C to +150°C
Operating Temperature . . . . . . . . . . . . . . . . . −55°C to +150°C
Lead Temperature (Soldering, 10 Sec.) . . . . . . . . . . . . . +300°C
Unless otherwise specified all voltages are with respect to
Ground. Currents are positive into, negative out of the specified terminal.
Consult Packaging Section of Unitrode Integrated Circuits databook for thermal limitations and considerations of packages.
PLCC-28 (Top View)
QP Package
RECOMMENDED OPERATING CONDITIONS
Termpwr Voltage . . . . . . . . . . . . . . . . . . . . . . . . . 4.0V to 5.25V
Signal Line Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to +3V
Disconnect Input Voltage . . . . . . . . . . . . . . . . . . 0V to Termpwr
* QP package pins 12 - 18 serve as both heatsink and signal
ground.
SOIC-28 (Top View)
DWP Package
DIL-24 (Top View)
N Package
* DWP package pin 28 serves as signal ground; pins 7, 8, 9,
20, 21, 22 serve as heatsink/ground.
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Note: Drawings are not to scale.
2
UC5602
ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for TA = 0°C to 70°C.
TRMPWR = 4.75V, DISCNCT = 0V. TA = TJ.
PARAMETER
Supply Current Section
Termpwr Supply Current
TEST CONDITIONS
MIN
All termination lines = Open
All termination lines = 0.5V
Power Down Mode
DISCNCT = Open
Output Section (Termination Lines)
Termination Impedance
∆ILINE = -5mA to -15mA
Output High Voltage
Max Output Current
Max Output Current
Output Leakage
Output Capacitance
Regulator Section
Regulator Output Voltage
Line Regulation
Load Regulation
Drop Out Voltage
Short Circuit Current
Sinking Current Capability
Thermal Shutdown
Disconnect Section
Disconnect Threshold
Threshold Hysteresis
Input Current
TJ = 25°C
0°C < TJ < 70°C
VTRMPWR = 4V (Note 1)
TJ = 25°C
0°C < TJ < 70°C
VLINE = 0.5V
TJ = 25°C
0°C < TJ < 70°C
VLINE = 0.5V, TRMPWR = 4V (Note 1)
TJ = 25°C
0°C < TJ < 70°C
TRMPWR = 0V to 5.25V VLINE = 0 to 4V
REG = 0V
VLINE = 5.25V
DISCNCT = 4V
TRMPWR = 0V to 5.25V, REG = Open
VLINE = 0V to 5.25V
DISCNCT = Open (Note 2)
102
97
2.6
2.55
-19.5
-18.5
-18.0
-17.0
TJ = 25°C
0°C < TJ < 70°C
2.7
2.55
TRMPWR = 4V to 6V
IREG = 0 to -400mA
All Termination Lines = 0.5V
VREG = 0V
VREG = 3.5V
MAX
UNITS
20
400
100
29
435
150
mA
mA
µA
110
10
118
129
3.1
3.2
-22.4
-22.4
-22.4
-22.4
400
100
400
Ω
Ω
V
V
mA
mA
mA
mA
nA
µA
nA
10
13
pF
2.9
3.1
3.2
20
50
1.2
-850
V
V
mV
mV
V
mA
mA
°C
1.7
V
mV
µA
2.9
-21.4
-21.5
10
-450
20
1.1
DISCNCT = 0V
TYP
10
20
1.0
-650
40
170
1.4
100
150
200
Note 1: Measuring each termination line while other 17 are low (0.5V).
Note 2: Guaranteed by design. Not 100% tested in production.
THERMAL DATA
DWP package: (see packaging section of UICC data book for more details on thermal performance)
Thermal Resistance Junction to Leads, θjL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18°C/W
Thermal Resistance Junction to Ambient, θja . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33°-43°C/W
N package:
Thermal Resistance Junction to Leads, θjL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50°C/W
Thermal Resistance Junction to Ambient, θja . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95°-105°C/W
QP package:
Thermal Resistance Junction to Leads, θjL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15°C/W
Thermal Resistance Junction to Ambient, θja . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30°-40°C/W
Note: The above numbers for θjL are maximums for the limiting thermal resistance of the package in a standard mounting configuration. The θja numbers are meant to be guidelines for the thermal performance of the device/pc-board system. All of the above
numbers assume no ambient airflow.
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3
UC5602
UDG-94053
Typical SCSI Bus Configuration Using the UC5602
A Look at the Response of a SCSI-2 Cable
Figure 1 shows a single line of a SCSI cable. The driver
is an open colletor type which when asserted pulls low,
and when negated the termination resistance serves as
the pull-up.
Figure 2 shows a worst case scenario of mid cable deassertion with a close proximity receiver. The voltage
VSTEP is defined as:
VSTEP = VOL +IO Z0
VOL =
IO
=
Z0 =
Driver Output Low Voltage
Current from Receiving Terminator
Cable Characteristic Impedance
IO =
UDG-94054
Figure 1. A Single Line of a SCSI Cable
VREG − VOL
110
In the pursuit of higher data rates, sampling could occur
during this step portion, therefore it is important to ensure
that the step is as high as possible to get the most noise
margin. For this reason the UC5602 is trimmed so that
the output current (IO) is as close as possible to the SCSI
max current spec of 22.4mA. The Termination impedance
is initially trimmed on the IC to 110 ohms typical, then the
regulator voltage is trimmed for the highest output current to within 22.4mA.
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UDG-94055
Figure 2. A Typical Response of a SCSI Cable
4
UC5602
Max Output Current vs. Temperature
VREF vs. Temperature
VREF vs. VIN
Output Impedance vs. Temperature
UNITRODE INTEGRATED CIRCUITS
7 CONTINENTAL BLVD. • MERRIMACK, NH 03054
TEL. (603) 424-2410 • FAX (603) 424 3460
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5
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