ETC UCC81510N

1
0
SLUS457B – JULY 2000 - REVISED OCTOBER 2000
Integrated 0.075-Ω Power MOSFET
3 V to 6 V Operation
External Analog Control of Fault Current
N and DP PACKAGES
(TOP VIEW)
VIN
VIN
VIN
GND*
GND*
FAULT
SHTDWN
IFAULT
From 0 A to 4 A
Independent Analog Control of Current
Limit up to 5 A
Fast Overload Protection
Unidirectional Switch
Minimal External Components
1-µA ICC When Disabled
Programmable On Time
Programmable Start Delay
Fixed 3% Duty Cycle
1
16
2
15
3
14
4
13
5
12
6
11
7
10
8
9
VOUT
VOUT
VOUT
GND*
GND*
NC
CT
IMAX
Pin 5 serves as the lowest impedance to the electrical
ground. Pins 4, 12, and 13, serve as heat sink/ground.
These pins should be connected to large etch PCB areas
to help dissipate heat. For N package, pins 4, 12, and 13,
are NC.
description
The UCC2918 low on-resistance hot swap power
manager provides complete power management, hot
swap capability, and circuit breaker functions. The only
VIN
components needed to operate the device, other than
VIN
supply bypassing, are a timing capacitor and two
VIN
programming resistors. All control and housekeeping
VIN
functions are integrated and externally programmable.
GND*
These include the fault current level, maximum output
GND*
sourcing current, maximum fault time, and startup
GND*
delay. In the event of a constant fault, the internal fixed
GND*
3% duty cycle ratio limits the average output power. The
GND*
IFAULT pin allows linear programming of the fault level
FAULT
current from 0 A to 4 A.
SHTDWN
Fast overload protection is accomplished by an
additional overload comparator. Its threshold is
internally set above the maximum sourcing current limit
setting. In the event of a short circuit or extreme current
condition, this comparator is tripped, shutting down the
output. This function is needed since the maximum
sourcing current limit loop has a finite bandwidth.
IFAULT
PWP PACKAGE
(TOP VIEW)
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
VOUT
VOUT
VOUT
VOUT
GND*
GND*
GND*
GND*
GND*
NC
CT
IMAX
Pin 9 serves as the lowest impedance to the electrical
ground. Pins 5, 6, 7, 8, 16, 17, 18, 19, and 20 serve as
heat sink/ground.
When the output current is below the fault level, the output MOSFET is switched on with a nominal resistance
of 0.075 Ω. When the output current exceeds the fault level or the maximum sourcing level, the output remains
on, but the fault timer starts charging a capacitor connected to the CT pin (CT). Once CT 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.
The UCC2918 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 termintation power (Termpwr). The UCC2918 can also be put into the sleep mode, drawing
only 1 µA of supply current.
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.
Copyright  2000, Texas Instruments Incorporated
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*+&) -))&+/ )',+#'& ()'**#&! '* &'+ &**)#$/ #&$,
+*+#&! ' $$ ()%+)*
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1
SLUS457B – JULY 2000 - REVISED OCTOBER 2000
description (continued)
Other features include an open-drain fault output indicator, thermal shutdown, undervoltage lockout, 3 V to 6 V
operation, and a low thermal resistance small-outline power package.
functional block diagram
CHARGE
PUMP
OVERLOAD
COMPARATOR
1 VIN
REVERSE
COMPARATOR
+
2 VIN
20mV
+
3 VIN
+
VOUT
+
CURRENT SENSE
H = OPEN
+
IMAX 9
MAXIMUM
CURRENT
LEVEL
CURRENT
FAULT LEVEL
OVERCURRENT
COMPARATOR
+
IFAULT 8
14 VOUT
ON TIME
CONTROL
15 VOUT
3% DUTY
CYCLE
16 VOUT
THERMAL
SHUTDOWN
1.5V
INTERNAL
BIAS
5
GND
4
13
12
HEAT SINK GND
PINS
10
6
CT
FAULT
+
7 SHTDWN
UDG–00101
absolute maximum ratings over operating free-air temperature (unless otherwise noted)†
Input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 V
SOIC power dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 W
Fault output sink current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 mA
Fault output voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VIN
Output current (dc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Internally Limited
Input voltage SHTDWN, IFAULT, IMAX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to VIN
Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –65C to 150C
Operating virtual junction temperature, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –55C to 150C
Lead temperature (soldering, 10 seconds) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300C
† 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.
‡ Unless otherwise indicated, voltages are reference to ground and currents are positive into, negative out of the specified terminal. Pulsed is
defined as a less than 10% duty cycle with a maximum duration of 500 µs. Consult Packaging Section of Databook for thermal limitations and
considerations of package.
2
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electrical characteristics at TA = –40°C to 85°C, VIN = 5 V, RIMAX = 42.2 kΩ, RIFAULT = 52.3 kΩ,
SHTDWN = 2.4 V, CT = 0.1 µF, TA = TJ (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
3
5
6
V
1
2
mA
0.5
5
µA
0.075
0.095
Ω
Supply Section
Voltage input range, VIN
VDD supply current
No load
Sleep mode current
SHTDWN = 0.2 V
Output Section
IOUT = 1 A to 4 A,
IOUT = 1 A to 4 A,
VIN = 5 V,
0.09
0.116
Ω
IOUT = 1 A to 4 A,
IOUT = 1 A to 4 A,
VIN = 5 V
0.075
0.125
Ω
VIN = 3 V
0.09
0.154
Ω
Reverse leakage current
SHTDWN = 0 V,
VIN = 0 V
20
µA
Initial start-up time
See Note 1
100
µs
Thermal shutdown
See Note 1
170
C
Thermal hysteresis
See Note 1
10
Output leakage
SHTDWN = 0.2 V
RDS(on)
Trip current
VIN = 3 V,
TA = 25°C
TA = 25°C
VOUT = 5 V
C
20
µA
RIFAULT = 105 kΩ
0.75
1
1.25
A
RIFAULT = 52.3 kΩ
1.7
2
2.3
A
RIFAULT = 34.8 kΩ
2.5
3
3.5
A
RIFAULT = 25.5 kΩ
3.3
4
4.7
A
RIMAX = 118 kΩ
0.3
1
1.7
A
1
2
3
A
RIMAX = 60.4 kΩ
RIMAX = 42.2 kΩ
2
3
4
A
RIMAX = 33.2 kΩ
2.5
3.8
5.1
A
RIMAX = 27.4 kΩ
3.0
4.6
6.2
A
–50
–36
–22
µA
CT discharge current
VCT = 1 V
VCT = 1 V
0.5
1.2
2.0
µA
Output duty cycle
VOUT = 0 V
1.5
3
6
%
CT fault threshold
0.8
1.3
1.8
V
CT reset threshold
0.25
0.5
0.75
V
1.5
2.0
output
Maximum out
ut current
Fault Section
CT charge current
Shutdown Section
Shutdown threshold
1.1
Shutdown hysteresis
100
V
mV
Input low current
SHTDWN = 0 V
–500
0
500
nA
Input high current
SHTDWN = 2 V
–2
–1
–0.5
µA
1
µA
0.4
0.9
V
Open Drain Fault Output Section
High level output current
Low level output voltage
IOUT = 1 mA
NOTE 1: Ensured by design. Not production tested.
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SLUS457B – JULY 2000 - REVISED OCTOBER 2000
pin descriptions
CT: A capacitor connected to this pin sets the maximum fault time. The maximum time must be greater than
the time to charge external load capacitance. The nominal fault time is defined as:
T
FAULT
22.2 10 3 C
T
(1)
Once the fault time is reached, the output shuts down for a time given by:
T
SD
0.667 10 6 C
T
(2)
This equates to a 3% duty cycle. The recommended minimum value for the CT capacitor is 0.1 µF.
FAULT: Open-drain output, which pulls low on any condition that causes the output to open; fault, thermal
shutdown, shutdown, and maximum sourcing current greater than the fault time.
GND: This is the most negative voltage in the circuit. All 4 ground pins should be used, and properly heat sunk
on the PCB.
IFAULT: A resistor connected from this pin to ground sets the fault threshold. The resistor versus fault current
is set by the formula:
R
FAULT
105 k
I
TRIP
(3)
IMAX: A resistor connected from this pin to ground sets the maximum sourcing current. The resistor vs the
output sourcing current is set by the formula:
R
IMAX
126 k
Maximum Sourcing Current
(4)
SHTDWN: When this pin is brought low, the IC is put into sleep mode. The input threshold is hysteretic, allowing
the user to program a startup delay with an external RC circuit.
VIN: This is the input voltage to the UCC2918. The recommended operating voltage range is 3V to 6V. All VIN
pins should be connected together and to the power source.
VOUT: Output voltage for the circuit breaker. When switched the output voltage will be approximately:
V
OUT
V
IN
0.075 I
OUT
.
(5)
All VOUT pins should be connected together and to the load.
4
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APPLICATION INFORMATION
HEAT SINK GND
PINS
4
VIN
D1
R1
CIN
1
VIN
2
VIN
3
VIN
6
FAULT
10
CT
12
GND
13
5
VOUT 14
VOUT 15
VOUT
RL
COUT
VOUT 16
RSD
CT
SHTDWN
IFAULT
IMAX
8
9
RIFAULT
7
S6
VIN
CSD
RIMAX
UDG–00102
Figure 1. Typical Application
protecting the UCC2918 from voltage transients
The parasitic inductance associated with the power distribution can cause a voltage spike at VIN if the load
current is suddenly interrupted by the UCC2918. It is important to limit the peak of this spike to less than 6 V
to prevent damage to the UCC2918. This voltage spike can be minimized by:
•
•
•
Reducing the power distribution inductance (e.g., twist the positive + and negative – leads of the power
supply feeding VIN, locate the power supply close to the UCC2918 or use a PCB ground plane).
Decoupling VIN with a capacitor, CIN (refer to Figure 1), located close to the VIN pin. This capacitor is
typically less than 1 µF to limit the inrush current.
Clamping the voltage at VIN below 6 V with a Zener diode, D1 (refer to Figure 1), located close to the VIN
pin.
estimating maximum load capacitance
For circuit breaker 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 circuit
breaker, the output comes up if the load requires less than the maximum available short-circuit current.
To ensure recovery of a duty-cycle of the current-limited circuit breaker from a short-circuited load condition,
there is a maximum total output capacitance that 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 CT.
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5
SLUS457B – JULY 2000 - REVISED OCTOBER 2000
APPLICATION INFORMATION
estimating maximum load capacitance
For worst-case constant-current load of value just less than the trip limit, COUT(max) can be estimated from:
C
I
I
MAX
OUT(max)
LOAD
22 10 3 C
V
OUT
T
(6)
Where VOUT is the output voltage and IMAX is the maximum sourcing current.
For a resistive load of value RLOAD, the value of COUT(max) can be estimated from:
22 10 3 C
T
C
OUT(max) 1
RLOAD n
1 VOUT I
R
MAX LOAD
(7)
UDG–00103
Figure 2. Load Curent, Timing Capacitor Voltage, and Output Voltage of the UCC2918 Under Fault
6
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TYPICAL CHARACTERISTICS
REVERSE VOLTAGE COMPARATOR
RESPONSE TIME
FAULT TIMING WAVEFORMS
VIN
COUT = 22 F
RLOAD = 5
CT (0.1 F)
CIN = 5 F
4A
RIFAULT = 52.3 k
RIMAX = 42.0 k
3A
FAULT OUT
VOUT = 0 V
2A
RLOAD = SHORT
CIN = 5 F
1A
RIFAULT = 52.3 k
IIN
RIMAX = 42.2 k
0A
OUTPUT CURRENT
Figure 3
Figure 4
NOTE: In Figure 3 the input driven with a pulse generator shows COUT discharging through RL and conducting through UCC81510 FET in the
reverse direction.
INRUSH CURRENT LIMITING
COUT = 22 F
VOUT
FAULT AND OUTPUT TURN-OFF
DELAY FROM CT FAULT
THRESHOLD
CT
RLOAD = 5
COUT = 0 F
CIN = 5 F
RIFAULT = 52.3 k
RIMAX = 60.4 k
RLOAD = 5
FAULT OUT
CIN = 5 F
VOUT
0V
IOUT (RLOAD = 5
0A
IINPUT @ 0.5 A/DIV
)
CT = OPEN
RIFAULT = 52.3 k
RIMAX = 42.4 k
Figure 5
Figure 6
NOTE: In Figure 5 the input is switched on through the external FET. VOUT shows IMAX linear amplifier limiting the changing current to COUT.
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7
SLUS457B – JULY 2000 - REVISED OCTOBER 2000
TYPICAL CHARACTERISTICS
PROPAGATION DELAY
SHUTDOWN TO FAULT AND
OUTPUT RAMP-DOWN
PROPAGATION DELAY
ENABLE TO FAULT AND
OUTPUT RAMP-UP
SHUTDOWN
SHUTDOWN
COUT = 0 F
FAULT OUT
FAULT OUT
RLOAD = 5
CIN = 5 F
COUT = 0 F
VOUT
RLOAD = 5
VOUT
RIFAULT = 52.3 k
CIN = 5 F
RIMAX = 42.4 k
1A
IOUT
RIFAULT = 52.3 k
IOUT (RLOAD = 5
RIMAX = 42.4 k
)
0A
Figure 7
Figure 8
ON-STATE RESISTANCE
vs
TEMPERATURE
ON-STATE RESISTANCE
vs
OUTPUT CURRENT
125
115
VIN = 5 V, I = 1 A
RDS(on) On–State Resistance – m
RDS(on) On–State Resistance – m
110
105
95
85
75
65
55
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
100
VIN = 3 V, I = 1 A
90
Average
80
70
VIN = 5 V, I = 4 A
60
50
VIN = 3 V, I = 4 A
40
– 40
40
Figure 10
Figure 9
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80
TA – Free-Air Temperature – C
IOUT – Output Current – A
8
0
• DALLAS, TEXAS 75265
120
SLUS457B – JULY 2000 - REVISED OCTOBER 2000
APPLICATION INFORMATION
safety considerations
Although the UCC2918 is designed to provide system protection for all fault conditions, all integrated circuits
can ultimately fall short. For this reason, if the UCC2918 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 power device. The UCC2918 prevents the fuse from blowing for virtually 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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9
IMPORTANT NOTICE
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any product or service without notice, and advise customers to obtain the latest version of relevant information
to verify, before placing orders, that information being relied on is current and complete. All products are sold
subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those
pertaining to warranty, patent infringement, and limitation of liability.
TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in
accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent
TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily
performed, except those mandated by government requirements.
Customers are responsible for their applications using TI components.
In order to minimize risks associated with the customer’s applications, adequate design and operating
safeguards must be provided by the customer to minimize inherent or procedural hazards.
TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent
that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other
intellectual property right of TI covering or relating to any combination, machine, or process in which such
semiconductor products or services might be or are used. TI’s publication of information regarding any third
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Copyright  2000, Texas Instruments Incorporated