UCC2912
UCC3912
PROGRAMMABLE HOT SWAP POWER MANAGER
SLUS241D - MARCH 1994 - REVISED NOVEMBER 2003
1
www.ti.com
D
Integrated 0.15-
Power MOSFET
D
3-V to 8-V Operation
D
Digital Programmable Current Limit
from 0 A to 3 A
D
Electronic Circuit Breaker Function
D
1
A I
CC
When Disabled
D
Programmable On-Time
D
Programmable Start Delay
D
Fixed 3% Duty Cycle
D
Unidirectional Switch
D
Thermal Shutdown
D
Fault-Output Indicator
D
Maximum-Output Current Can Be Set to 1 A
Above the Programmed Fault Level or to a
Full 4 A
D
Power SOIC, Low-Thermal Resistance
Packaging
description
The UCC3912 family of hot swap power managers provides complete power management, hot swap capability,
and circuit breaker functions. The only component required to operate the device, other than supply bypassing,
is the fault timing capacitor, C
T
. All control and housekeeping functions are integrated, and externally
programmable. These include the fault current level, maximum output-sourcing current, maximum fault time,
and startup delay. In the event of a constant fault, the internal fixed 3% duty cycle ratio limits average output
power.
The internal 4-bit DAC allows programming of the fault level current from 0 A to 3 A with 0.25-A resolution. The
IMAX control pin sets the maximum sourcing current to 1 A above the fault level when driven low, and to a full
4 A when driven high for applications which require fast output capacitor charging.
When the output current is below the fault level, the output MOSFET is switched on with a nominal on resistance
of 0.15
. When the output current exceeds the fault level, but is less than the maximum sourcing level, the
output remains switched on, but the fault timer starts charging C
T
. Once C
T
charges to a preset threshold, the
switch is turned off, and remains off for 30 times the programmed fault time. When the output current reaches
the maximum sourcing level, the MOSFET transitions from a switch to a constant current source. (continued)
block diagram
UDG-99146
B1
B0
6
7
8
2
3
9
11
16
0 A-3 A
0.25
RES
B3
B2
5
4
13
12
CT
ON TIME
CONTROL
3% DUTY
CYCLE
+
-
THERMAL
SHUTDOWN
INTERNAL
BIAS
+
-
1
SHTDWN
14
15
1.5 V
H = OPEN
FAULT
CURRENT SENSE
+
-
+
CHARGE
PUMP
30 mV
VOUT
REVERSE VOLTAGE
COMPARATOR
+
-
LINEAR CURRENT AMPLIFIER
1 A
ABOVE
FAULT
10
IMAX
GND
HEATSINK
GND PINS
CURRENT FAULT
LEVEL 0A TO 3 A
OVERCURRENT
COMPARATOR
MAX CURRENT
LEVEL
4 A
H = 4 A
VIN
VIN
VOUT
VOUT
POWER
FET
4 BIT DAC
Copyright
2003, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
UCC2912
UCC3912
PROGRAMMABLE HOT SWAP POWER MANAGER
SLUS241D - MARCH 1994 - REVISED NOVEMBER 2003
2
www.ti.com
description (continued)
The UCC3912 family is designed for unidirectional current flow, emulating an ideal diode in series with the power
switch. This feature is particularly attractive in applications where many devices are powering a common bus,
such as with SCSI Termpwr.
The UCC3912 family can be put into sleep mode drawing only 1-
A of supply current. The SHTDWN pin has
a preset threshold hysteresis which allows the user the ability to set a time delay upon startup to achieve
sequencing of power. Other features include an open drain FAULT output indicator, thermal shutdown, under
voltage lockout, and a low thermal resistance small outline package.
absolute maximum ratings over operating free-air temperature (unless otherwise noted)
}
VIN
8 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FAULT sink current
50 mA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FAULT voltage
-0.3 to V
IN
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output current
Self Limiting
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input voltage
(B0, B1, B2, B3, IMAX, SHTDWN)
-0.3 to V
IN
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage temperature range, T
stg
-65
C to 150
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating junction temperature range, T
J
-55
C to 150
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lead temperature (soldering, 10 sec.)
300
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
Currents are positive into, negative out of the specified terminal. Consult Packaging Section of the Interface Products Data book (TI Literature
Number SLUD002) for thermal limitations and considerations of packages.
package information
DIL-16, SOIC-16
N, DP Package
(TOP VIEW)
TSSOP-24,
PWP Package
(TOP VIEW)
*Pin 5 serves as lowest impedance to the electrical
ground; Pins 4, 12, and 13 serve as heat sink/ground.
These pins should be connected to large etch areas to
help dissipate heat. For N package, pins 4, 12, and 13
are N/C.
*Pin 9 serves as lowest impedance to the electrical ground;
other GND pins serve as heat sink/ground. These pins should
be connected to large etch areas to help dissipate heat.
B3
VOUT
GND*
GND*
FAULT
N/C
EGND*
GND*
GND*
VIN
VIN
GND*
SHTDWN
GND*
B2
GND*
GND*
CT
12
11
10
9
8
7
6
5
4
3
2
1
13
14
15
16
17
18
19
20
21
22
23
24
IMAX
N/C
VOUT
B1
B0
GND*
UCC2912
UCC3912
PROGRAMMABLE HOT SWAP POWER MANAGER
SLUS241D - MARCH 1994 - REVISED NOVEMBER 2003
3
www.ti.com
electrical characteristics, these specifications apply for T
A
= -40
C to 85
C for the UCC2912;
T
A
= 0
C to 70
C for the UCC3912, VIN = 5 V, IMAX = 0.4 V, SHTDWN = 2.4 V
(unless otherwise stated)
supply section
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
Voltage input range
3.0
8.0
V
Supply current
1.0
2.0
mA
Sleep mode current
SHTDWN = 0.2 V
0.5
5.0
A
NOTE 1: All voltages are with respect to ground. Current is positive into and negative out of the specified terminal.
output section
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
IOUT = 1 A
0.15
0.22
V
IOUT = 2 A
0.3
0.45
V
Voltage drop
IOUT = 3 A
0.45
0.68
V
Voltage drop
IOUT = 1A,
VIN = 3 V
0.17
0.27
V
IOUT = 2 A,
VIN = 3 V
0.35
0.56
V
IOUT = 3 A,
VIN = 3 V
0.5
0.8
V
Reverse leakage current
VIN < VOUT ,
SHTDWN = 0.2 V, VOUT = 5 V
5
20
A
Initial startup time
See Note 2
100
s
Short circuit response
See Note 2
100
ns
Thermal shutdown
See Note 2
170
C
Thermal hysteresis
See Note 2
10
C
NOTE 1: All voltages are with respect to ground. Current is positive into and negative out of the specified terminal.
NOTE 2: Ensured by design. Not production tested.
DAC section
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
Output leakage
Code = 0000-0011
0
20
A
Code = 0100
0.1
0.25
0.45
A
Code = 0101
0.25
0.50
0.75
A
Code = 0110
0.5
0.75
1.0
A
Code = 0111
0.75
1.00
1.25
A
Code = 1000
1.0
1.25
1.5
A
Trip current
Code = 1001
1.25
1.50
1.75
A
Trip current
Code = 1010
1.5
1.75
2.0
A
Code = 1011
1.7
2.00
2.3
A
Code = 1100
1.9
2.25
2.58
A
Code = 1101
2.1
2.50
2.9
A
Code = 1110
2.3
2.75
3.2
A
Code = 1111
2.5
3.0
3.5
A
Maximum output current
Code = 0000 to 0011
0.02
mA
Maximum output current over trip
UCC2912
Code = 0100 to 1111,
IMAX = 0 V
0.5
1.0
2.0
A
Maximum output current over trip
(current source mode)
UCC3912
Code = 0100 to 1111,
IMAX = 0 V
0.5
1.0
1.8
A
Maximum output current (current source mode)
Code = 0100 to 1111,
IMAX = 2.4 V
3.0
4.0
5.2
A
NOTE 1: All voltages are with respect to ground. Current is positive into and negative out of the specified terminal.
UCC2912
UCC3912
PROGRAMMABLE HOT SWAP POWER MANAGER
SLUS241D - MARCH 1994 - REVISED NOVEMBER 2003
4
www.ti.com
electrical characteristics, these specifications apply for T
A
= -40
C to 85
C for the UCC2912;
T
A
= 0
C to 70
C for the UCC3912, VIN = 5 V, IMAX = 0.4 V, SHTDWN = 2.4 V
(unless otherwise stated)
timer section
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
CT charge current
VCT = 1.0 V
-45.0
-36.0
-22.0
A
CT discharge current
UCC2912
VCT = 1.0 V
0.72
1.20
1.57
A
CT discharge current
UCC3912
VCT = 1.0 V
0.72
1.20
1.50
A
Output duty cycle
VOUT = 0 V
2.0
3.0
6.0
%
CT fault threshold
1.3
1.5
1.7
V
CT reset threshold
0.4
0.5
0.6
V
NOTE 1: All voltages are with respect to ground. Current is positive into and negative out of the specified terminal.
shutdown section
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
Shutdown threshold
1.1
1.5
1.9
V
Shutdown hysteresis
100
mV
Input current
SHTDWN = 1 V
100
500
nA
fault output section
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
Output leakage current
500
nA
Low level output voltage
IOUT = 10 mA
0.4
0.8
V
TTL input dc characteristics section
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
TTL input voltage high
(can be connected to VIN)
2.0
V
TTL input voltage low
0.8
V
TTL input high current
VIH = 2.4 V
3
10
A
TTL input low current
VIL = 0.4 V
1
A
NOTE 1: All voltages are with respect to ground. Current is positive into and negative out of the specified terminal.
pin description
B0-B3: These pins provide digital input to the DAC which sets the fault current threshold. They can be used
to provide a digital soft-start, adaptive current limiting.
CT: A capacitor connected to ground sets the maximum fault time. The maximum fault time must be more than
the time to charge the external capacitance in one cycle. The maximum fault time is defined as
FAULT = 27.8
10
3
CT. Once the fault time is reached the output will shutdown for a time given by:
T
SD
= 833
10
3
CT, this equates to a 3% duty cycle.
FAULT: Open drain output which pulls low upon any condition which causes the output to open: fault, thermal
shutdown, or shutdown.
IMAX: When this pin is set to logic low the maximum sourcing current will always be 1 A above the programmed
fault level. When set to logic high, the maximum sourcing current will be a constant 4 A for applications which
require fast charging of load capacitance.
UCC2912
UCC3912
PROGRAMMABLE HOT SWAP POWER MANAGER
SLUS241D - MARCH 1994 - REVISED NOVEMBER 2003
5
www.ti.com
pin description (continued)
SHTDWN: When this pin is brought to a logic low, the IC is put into a sleep mode drawing typically less than
1
A of I
CC
. The input threshold is hysteretic, allowing the user to program a startup delay with an external RC
circuit.
VIN: Input voltage to the UCC3912. The recommended voltage range is 3 V to 8 V. Both VIN pins should be
connected together and to the power source.
VOUT: Output voltage from the UCC3912. When switched the output voltage will be approximately
V
IN
-
(0.15
I
OUT
). Both VOUT pins should be connected together and to the load.
APPLICATION INFORMATION
UDG-99171
NOTE: For demonstration board schematic see Design Note DN-58 (TI Literature Number SLUA187).
6
7
8
9
11
10
B0
B1
B2
B3
IMAX
16
3
2
4
12
13
5
14
15
1
SHTDWN
VOUT
VIN
FAULT
CT
GND
HEAT SINK
GND PINS
RL
COUT
VOUT
CSD
RSD
VIN
CIN
R1
LED
D1
CT
S1
S2
S3
S4
S5
DIP
SWITCH
S6
VIN
VIN
UCC2912
UCC3912
Figure 1. Evaluation Circuit
protecting the UCC3912 from voltage transients
The parasitic inductance associated with the power distribution can cause a voltage spike at V
IN
if the load
current is suddenly interrupted by the UCC3912. It is important to limit the peak of this spike to less than 8 V
to prevent damage to the UCC3912. This voltage spike can be minimized by:
D
Reducing the power distribution inductance (e.g., twist the positive and negative leads of the power supply
feeding V
IN
, locate the power supply close to the UCC3912, use a PCB ground plane,...etc.).
D
Decoupling V
IN
with a capacitor, C
IN
(refer to Figure 1), located close to pins 2 and 3. This capacitor is
typically less than 1
F to limit the inrush current.
D
Clamping the voltage at V
IN
below 8 V with a zener diode, D1 (refer to Figure 1), located close to pins 2
and 3.
UCC2912
UCC3912
PROGRAMMABLE HOT SWAP POWER MANAGER
SLUS241D - MARCH 1994 - REVISED NOVEMBER 2003
6
www.ti.com
APPLICATION INFORMATION
UDG-93019-4
Figure 2. Load Current, Timing-Capacitor Voltage, and Output Voltage of the UCC3912 Under Fault
Conditions.
estimating maximum load capacitance
For hot-swap applications, the rate at which the total output capacitance can be charged depends on the
maximum output current available and the nature of the load. For a constant-current current-limited controller,
the output will come up if the load asks for less than the maximum available short-circuit current.
To ensure recovery of a duty-cycle from a short-circuited load condition, there is a maximum total output
capacitance which can be charged for a given unit ON time (fault time). The design value of ON or fault time
can be adjusted by changing the timing capacitor C
T
.
For worst-case constant-current load of value just less than the trip limit; C
OUT(max)
can be estimated from:
C
OUT(max)
[
I
MAX
*
I
LOAD
28
103
CT
V
OUT
where V
OUT
is the output voltage.
UCC2912
UCC3912
PROGRAMMABLE HOT SWAP POWER MANAGER
SLUS241D - MARCH 1994 - REVISED NOVEMBER 2003
7
www.ti.com
APPLICATION INFORMATION
For a resistive load of value RL, the value of C
OUT(max)
can be estimated from:
C
OUT(max)
[
28
103
CT
RL
n
1
1
*
V
OUT
I
MAX
RL
The overcurrent comparator senses both the DAC output and a representation of the output current. When the
output current exceeds the programmed level the timing capacitor C
T
charges with 36
A of current. If the fault
occurs for the time it takes for C
T
to charge up to 1.5 V, the fault latch is set and the output switch is opened.
The output remains opened until C
T
discharges to 0.5 V with a 1.2-
A current source. Once the 0.5 V is reached
the output is enabled and will either appear as a switch, if the fault is removed, or a current source if the fault
remains. If the over current condition is still present, then C
T
will begin charging, starting the cycle over, resulting
in approximately a 3% on time.
UDG-94019-1
Figure 3. UCC3912 On-Time Circuitry
UCC2912
UCC3912
PROGRAMMABLE HOT SWAP POWER MANAGER
SLUS241D - MARCH 1994 - REVISED NOVEMBER 2003
8
www.ti.com
APPLICATION INFORMATION
UDG-94019-1
Figure 4. R
DS(on)
vs. Temperature at 2-A Load Current.
safety recommendations
Although the UCC3912 family is designed to provide system protection for all fault conditions, all integrated
circuits can ultimately fail short. For this reason, if the UCC3912 is intended for use in safety critical applications
where UL or some other safety rating is required, a redundant safety device such as a fuse should be placed
in series with the device. The UCC3912 will prevent the fuse from blowing virtually for all fault conditions,
increasing system reliability and reducing maintenance cost, in addition to providing the hot swap benefits of
the device.
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accordance with TI's standard warranty. Testing and other quality control techniques are used to the extent TI
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