UCC3912PWPTRG4 [TI]
Programmable Hot Swap Power Manager; 可编程热插拔电源管理器
| 型号： | UCC3912PWPTRG4 |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | Programmable Hot Swap Power Manager |
| 文件： | 总6页 (文件大小：151K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
application
INFO
UCC3912
available
Programmable Hot Swap Power Manager
FEATURES
DESCRIPTION
• Integrated 0.15Ω Power MOSFET
The UCC3912 Hot Swap Power Manager provides complete power man-
agement, hot swap capability, and circuit breaker functions. The only com-
ponent required to operate the device, other than supply bypassing, is the
fault timing capacitor, CT. All control and housekeeping functions are inte-
grated, and externally programmable. These include the fault current level,
maximum output sourcing current, maximum fault time,and start-up delay.
In the event of a constant fault, the Internal fixed 3% duty cycle ratio limits
average output power.
• 3V to 8V Operation
• Digital Programmable Current Limit
from 0 to 3A
• Electronic Circuit Breaker Function
• 1µA ICC when Disabled
• Programmable on Time
• Programmable Start Delay
• Fixed 3% Duty Cycle
The internal 4 bit DAC allows programming of the fault level current from 0
to 3A with 0.25A resolution. The IMAX control pin sets the maximum sour-
cing current to 1A above the fault level when driven low, and to a full 4A
when driven high for applications which require fast output capacitor charg-
ing.
• Uni-Directional Switch
• Thermal Shutdown
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 cur-
rent exceeds the fault level, but is less than the maximum sourcing level,
the output remains switched on, but the fault timer starts charging CT.
Once CT charges to a preset threshold, the switch is turned off, and re-
mains 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.
• Fault Output Indicator
• Maximum Output Current can be set
to 1A above the Programmed Fault
Level or to a full 4A
• Power SOIC, Low Thermal
Resistance Packaging
(continued)
BLOCK DIAGRAM
2
REVERSE VOLTAGE
30mV
COMPARATOR
VIN
CHARGE
PUMP
H = 4A
IMAX 10
3
V
OUT
MAX
CURRENT
LEVEL
CURRENT SENSE
H = OPEN
4A
POWER
FET
LINEAR CURRENT
AMPLIFIER
1A
ABOVE
FAULT
14
15
OVER CURRENT
COMPARATOR
VOUT
ON TIME
CONTROL
CURRENT FAULT
LEVEL 0–3 AMPS
3% DUTY
CYCLE
THERMAL
SHUTDOWN
1.5V
0–3A
+
–
0.25
RES
INTERNAL
BIAS
1
SHTDWN
6
7
8
9
5
4
13
12
11
16
HEAT SINK
GND PINS
B3
B2
B1
B0
GND
CT
FAULT
UDG-99146
4 BIT DAC
SLUS241A - NOVEMBER 1999
UCC3912
ABSOLUTE MAXIMUM RATINGS
DESCRIPTION (cont.)
VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +8 V
FAULT Sink Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50mA
FAULT Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 to VIN
Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Limiting
Input Voltage
(B0, B1, B2, B3, IMAX, SHTDWN) . . . . . . . . . . . –0.3 to VIN
Storage Temperature Range . . . . . . . . . . . . . –65°C to +150°C
Operating Junction Temperature Range . . . . –55°C to +150°C
Lead Temperature (Soldering, 10 sec.) . . . . . . . . . . . . . +300°C
The UCC3912 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 can be put into sleep mode drawing only
1µA of supply current. The SHTDWN pin has a preset
threshold hysteresis which allows the user the ability to
set a time delay upon start-up to achieve sequencing of
power. Other features include an open drain FAULT out-
put indicator, Thermal Shutdown, Under Voltage Lock-
out, and a low thermal resistance Small outline package.
Currents are positive into, negative out of the specified termi-
nal. Consult Packaging Section of Databook for thermal limita-
tions and considerations of packages.
CONNECTION DIAGRAMS
TSSOP-24 (Top View)
PWP Package
DIL-16, SOIC-16 (Top View)
N, DP Package
SHTDWN
VIN
1
2
3
4
5
6
7
8
9
24 FAULT
23 VOUT
22 VOUT
21 N/C
VIN
N/C
GND*
GND*
GND*
GND*
EGND*
20 GND*
19 GND*
18 GND*
17 GND*
16 GND*
15 CT
B3 10
B2 11
B1 12
14 IMAX
13 B0
*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.
ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for TJ = 0°C to 70°C, VIN = 5V,
IMAX = 0.4V, SHTDWN = 2.4V.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX UNITS
Supply Section
Voltage Input Range
Supply Current
3.0
8.0
2.0
5.0
V
1.0
0.5
mA
µA
Sleep Mode Current
Output Section
Voltage Drop
SHTDWN = 0.2V
IOUT = 1A
0.15
0.3
0.22
0.45
0.68
0.27
0.56
0.8
V
V
V
V
V
V
I
I
I
OUT = 2A
OUT = 3A
0.45
0.17
0.35
0.5
OUT = 1A, VIN = 3V
IOUT = 2A, VIN = 3V
I
OUT = 3A, VIN = 3V
2
UCC3912
ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for TJ = 0°C to 70°C, VIN = 5V,
IMAX = 0.4V, SHTDWN = 2.4V.
PARAMETER
Output Section (cont.)
TEST CONDITIONS
MIN
TYP
MAX UNITS
Reverse Leakage Current
VIN < VOUT , SHTDWN = 0.2V,
5
20
µA
V
OUT = 5V
Initial Start-up Time
Short Circuit Response
Thermal Shutdown
Thermal Hysteresis
DAC Section
(Note 2)
(Note 2)
(Note 2)
(Note 2)
100
100
170
10
µs
ns
°C
°C
Output Leakage
Code = 0000-0011
Code = 0100
0
20
0.45
0.75
1.0
µA
A
Trip Current
0.1
0.25
0.5
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
2.50
2.75
3.0
Code = 0101
A
Code = 0110
A
Code = 0111
0.75
1.0
1.25
1.5
A
Code = 1000
A
Code = 1001
1.25
1.5
1.75
2.0
A
Code = 1010
A
Code = 1011
1.7
2.3
A
Code = 1100
1.9
2.58
2.9
A
Code = 1101
2.1
A
Code = 1110
2.3
3.2
A
Code = 1111
2.5
3.5
A
Max Output Current
Code = 0000 to 0011
Code = 0100 to 1111, IMAX = 0V
0.02
1.8
mA
A
Max Output Current Over Trip (Current Source
Mode)
0.5
3.0
1.0
4.0
Max Output Current (Current Source Mode)
Timer Section
Code = 0100 to 1111, IMAX = 2.4V
5.2
A
CT Charge Current
VCT = 1.0V
−45.0 −36.0 −22.0
µA
µA
%
V
CT Discharge Current
Output Duty Cycle
VCT = 1.0V
0.72
2.0
1.3
0.4
1.2
3.0
1.5
0.5
1.5
6.0
1.7
0.6
VOUT = 0V
CT Fault Threshold
CT Reset Threshold
V
Shutdown Section
Shutdown Threshold
1.1
1.5
100
100
1.9
V
Shutdown Hysteresis
Input Current
mV
nA
SHTDWN = 1V
500
Fault Output Section
Output Leakage Current
Low Level Output Voltage
TTL Input DC Characteristics Section
TTL Input Voltage High
TTL Input Voltage Low
TTL Input High Current
TTL Input Low Current
500
0.8
nA
V
IOUT = 10mA
0.4
(can be connected to VIN)
2.0
V
V
0.8
10
1
V
IH = 2.4V
IL = 0.4V
3
µA
µA
V
Note 1: All voltages are with respect to Ground. Current is positive into and negative out of the specified terminal.
Note 2: Guaranteed by design. Not 100% tested in production.
3
UCC3912
PIN DESCRIPTIONS
grammed fault level. When set to logic high, the maxi-
mum sourcing current will be a constant 4A for
applications which require fast charging of load capaci-
tance.
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 •103
• CT. Once the fault time is reached the output will shut-
down for a time given by: TSD = 833 •103 • CT, this
equates to a 3% duty cycle.
SHTDWN: When this pin is brought to a logic low, the IC
is put into a sleep mode drawing typically less than 1µA
of ICC. The input threshold is hysteretic, allowing the user
to program a start-up delay with an external RC circuit.
VIN: Input voltage to the UCC3912. The recommended
voltage range is 3 to 8 volts. Both VIN pins should be
connected together and to the power source.
FAULT: Open drain output which pulls low upon any con-
dition which causes the output to open: Fault, Thermal
Shutdown, or Shutdown.
VOUT: Output voltage from the UCC3912. When
switched the output voltage will be approximately VIN -
(0.15Ω • IOUT). Both VOUT pins should be connected to-
gether and to the load.
IMAX: When this pin is set to logic low the maximum
sourcing current will always be 1A above the pro-
APPLICATION INFORMATION
4
12
13
5
GND
HEAT SINK
GND PINS
V
V
OUT
IN
2
14
15
VIN
VOUT
R1
C
R
L
C
OUT
IN
3
D1
UCC3912
LED
R
V
SD
IN
S6
16 FAULT
11 CT
SHTDWN
1
C
SD
B0
B1
7
B2
8
B3 IMAX
C
T
6
9
5
V
IN
DIP
SWITCH
S1
S2
S3
S4
S5
UDG-99171
Note: For demonstration board schematic see Design Note DN-58.
Figure 1. Evaluation circuit.
• Reducing the power distribution inductance (e.g., twist
the “+” and “–” leads of the power supply feeding VIN,
locate the power supply close to the UCC3912, use a
PCB ground plane,...etc.).
Protecting The UCC3912 From Voltage Transients
The parasitic inductance associated with the power distri-
bution can cause a voltage spike at VIN if the load current
is suddenly interrupted by the UCC3912. It is important to
limit the peak of this spike to less than 8V to prevent
damage to the UCC3912. This voltage spike can be mini-
mized by:
• Decoupling VIN with a capacitor, CIN (refer to Fig. 1),
located close to pins 2 and 3. This capacitor is typically
less than 1µF to limit the inrush current.
• Clamping the voltage at VIN below 8V with a Zener
diode, D1(refer to Fig. 1), located close to pins 2 and 3.
4
UCC3912
APPLICATION INFORMATION (cont.)
UDG-93019-4
Figure 2. Load current, timing capacitor voltage, and output voltage of the UCC3912 under Fault conditions.
where VOUT is the output voltage.
Estimating Maximum Load Capacitance
For a resistive load of value RL, the value of COUT(max) can
be estimated from:
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 guarantee 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 ca-
pacitor CT.
28 •103 •CT
COUT max
≈
)
(
1
RL• ln
VOUT
1−
I
•RL
For worst-case constant-current load of value just less
than the trip limit; COUT(max) can be estimated from:
MAX
3
28 •10 •CT
COUT(max) ≈ I
−ILOAD •
(
)
MAX
VOUT
5
UCC3912
APPLICATION INFORMATION (cont.)
The overcurrent comparator senses both the DAC output
and a representation of the output current. When the out-
put current exceeds the programmed level the timing ca-
1.2µA current source. Once the 0.5V is reached the out-
put is enabled and will either appear as a switch, if the
fault is removed, or a current source if the fault remains.
pacitor CT charges with 36µA of current. If the fault If the over current condition is still present then CT will
occurs for the time it takes for CT to charge up to 1.5V, begin charging, starting the cycle over, resulting in ap-
the fault latch is set and the output switch is opened. The proximately a 3% on time.
output remains opened until CT discharges to 0.5V with a
UDG-94019-1
Figure 3. UCC3912 on time control circuitry.
SAFETY RECOMMENDATIONS
Although the UCC3912 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 all fault conditions, increasing system
reliability and reducing maintainence cost, in addition to
providing the hot swap benefits of the device.
UDG-94101
Figure 4. RDS(on) vs temperature at 2A load current.
UNITRODE CORPORATION
7 CONTINENTAL BLVD. • MERRIMACK, NH 03054
TEL. (603) 424-2410 FAX (603) 424-3460
6
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