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UCC3918 LOW ON-RESISTANCE HOT SWAP POWER MANAGER
SLUS384B -- NOVEMBER 1999 -- REVISED JUNE 2000
D Integrated 0.075-W Power MOSFET D 3 V to 6 V Operation D External Analog Control of Fault Current
from 0 A to 4 A Limit Up to 5 A
N and DP PACKAGES (TOP VIEW)
D Independent Analog Control of Current D D D D D D D
Fast Overload Protection Unidirectional Switch Minimal External Components 1-mA ICC When Disabled Programmable On Time Programmable Start Delay Fixed 3% Duty Cycle
VIN VIN VIN GND* GND* FAULT SHTDWN IFAULT
1 2 3 4 5 6 7 8
16 15 14 13 12 11 10 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 UCC3918 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 W. 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 UCC3918 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 UCC3918 can also be put into the sleep mode, drawing only 1 mA 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.
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.
Copyright a 2000, Texas Instruments Incorporated
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1
UCC3918 LOW ON-RESISTANCE HOT SWAP POWER MANAGER
SLUS384B -- NOVEMBER 1999 -- REVISED JUNE 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 REVERSE COMPARATOR + 20mV 1 VIN 2 VIN 3 VIN VOUT CURRENT SENSE H = OPEN
+
+
+
IMAX 9 MAXIMUM CURRENT LEVEL
+
OVERCURRENT CURRENT COMPARATOR FAULT LEVEL + IFAULT 8
ON TIME CONTROL 3% DUTY CYCLE THERMAL SHUTDOWN INTERNAL BIAS +
14 VOUT 15 VOUT 16 VOUT 1.5V 7 SHTDWN
5 GND
4
13
12
10 CT
6 FAULT
UDG--99153
HEAT SINK GND PINS
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . --65_C to 150_C Operating virtual junction temperature TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . --55_C to 150_C Lead temperature (soldering, 10 seconds) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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. 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 ms. Consult Packaging Section of Databook for thermal limitations and considerations of package.
2
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UCC3918 LOW ON-RESISTANCE HOT SWAP POWER MANAGER
SLUS384B -- NOVEMBER 1999 -- REVISED JUNE 2000
electrical characteristics at TA = 0C to 70C, VIN = 5 V, RIMAX = 42.2 kW, RIFAULT = 52.3 kW, SHTDWN = 2.4 V, TA = TJ (unless otherwise noted)
PARAMETER Supply Section Voltage input range, VIN VDD supply current Sleep mode current Output Section IOUT = 1 A to 4 A, RDS(on) IOUT = 1 A to 4 A, IOUT = 1 A to 4 A, IOUT = 1A to 4A, Reverse leakage current Initial startup time Thermal shutdown Thermal hysteresis Output leakage SHTDWN = 0 V, See Note 1 See Note 1 See Note 1 SHTDWN = 0.2 V RIFAULT = 105 kW Trip current RIFAULT = 52.3 kW RIFAULT = 34.8 kW RIFAULT = 25.5 kW RIMAX = 118 kW RIMAX = 60.4 kW Maximum output current RIMAX = 42.2 kW RIMAX = 33.2 kW RIMAX = 27.4 kW Fault Section CT charge current CT discharge current Output duty cycle CT fault threshold CT reset threshold Shutdown Section Shutdown threshold Shutdown hysteresis Input low current Input high current Open Drain Fault Output Section High level output current Low level output voltage IOUT = 1mA 0.4 NOTE 1: Ensured by design. Not production tested. 1 0.9 mA V SHTDWN = 0V SHTDWN = 2V -500 -2 1.1 1.5 100 0 -1 500 -0.5 2.0 V mV nA mA VCT = 1 V VCT = 1 V VOUT = 0 V -50 0.5 1.5 0.8 0.25 -36 1.2 3 1.3 0.5 -22 2.0 6 1.8 0.75 mA mA % V V 0.75 1.7 2.5 3.3 0.3 1 2 2.5 3.0 1 2 3 4 1 2 3 3.8 4.6 VIN = 5 V, VIN = 3 V, VIN = 5 V VIN = 3 V VIN = 0 V VOUT = 5 V 100 170 10 20 1.25 2.3 3.5 4.7 1.7 3 4 5.1 6.2 TA = 25C TA = 25C 0.075 0.09 0.075 0.09 0.095 0.116 0.125 0.154 20 W W W W mA ms _C _C mA A A A A A A A A A No load SHTDWN = 0.2 V 3 5 1 0.5 6 2 5 V mA mA TEST CONDITIONS MIN TYP MAX UNITS
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UCC3918 LOW ON-RESISTANCE HOT SWAP POWER MANAGER
SLUS384B -- NOVEMBER 1999 -- REVISED JUNE 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 x 10 3 x C T (1)
Once the fault time is reached the output shuts down for a time given by: T SD = 0.667 x 10 6 x C T (2)
This equates to a 3% duty cycle. The recommended minimum value for the CT capacitor is 0.1 mF. 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 UCC3918. 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 x I OUT . (5)
All VOUT pins should be connected together and to the load.
4
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UCC3918 LOW ON-RESISTANCE HOT SWAP POWER MANAGER
SLUS384B -- NOVEMBER 1999 -- REVISED JUNE 2000
APPLICATION INFORMATION
HEAT SINK GND PINS 4 1 VIN D1 R1 CIN 2 3 6 10 CT VIN VIN VIN FAULT CT IFAULT 8 RIFAULT IMAX 9 RIMAX
UDG--99152
GND 5
12
13
VOUT 14 VOUT 15 VOUT 16 SHTDWN 7 S6 CSD RSD RL COUT
VOUT
VIN
Figure 1. Typical Application
protecting the UCC3918 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 UCC3918. It is important to limit the peak of this spike to less than 6 V to prevent damage to the UCC3918. 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 UCC3918 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 mF 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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UCC3918 LOW ON-RESISTANCE HOT SWAP POWER MANAGER
SLUS384B -- NOVEMBER 1999 -- REVISED JUNE 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 OUT(max) =I
MAX - ILOAD
22 x 10 3 x 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:
3xC 22 x 10 T C = OUT(max) R 1 LOAD x n1- VOUT IMAXxRLOAD
(7)
UDG--97071
Figure 2. Load Curent, Timing Capacitor Voltage and Output Voltage of the UCC3918 Under Fault
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UCC3918 LOW ON-RESISTANCE HOT SWAP POWER MANAGER
SLUS384B -- NOVEMBER 1999 -- REVISED JUNE 2000
TYPICAL CHARACTERISTICS
REVERSE VOLTAGE COMPARATOR RESPONSE TIME FAULT TIMING WAVEFORMS
VIN COUT = 22 mF RLOAD = 5 W 4A 3A 2A 1A 0A IIN CIN = 5 mF RIFAULT = 52.3 kW W RIMAX = 42.0 kW W FAULT OUT VOUT = 0 V RLOAD = SHORT CIN = 5 mF RIFAULT = 52.3 kW W RIMAX = 42.2 kW W OUTPUT CURRENT CT (0.1 mF)
Figure 3
INRUSH CURRENT LIMITING
Figure 4
FAULT AND OUTPUT TURN-OFF DELAY FROM CT FAULT THRESHOLD CT COUT = 0 mF RLOAD = 5 W FAULT OUT VOUT CIN = 5 mF
COUT = 22 mF VOUT RLOAD = 5 W CIN = 5 mF RIFAULT = 52.3 kW W RIMAX = 60.4 kW W 0V
IOUT (RLOAD = 5 W) 0A IINPUT @ 0.5 A/DIV CT = OPEN RIFAULT = 52.3 kW W RIMAX = 42.4 kW W
Figure 5
Figure 6
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7
UCC3918 LOW ON-RESISTANCE HOT SWAP POWER MANAGER
SLUS384B -- NOVEMBER 1999 -- REVISED JUNE 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 mF RLOAD = 5 W CIN = 5 mF
FAULT OUT
FAULT OUT
COUT = 0 mF RLOAD = 5 W CIN = 5 mF
VOUT
VOUT 1A
RIFAULT = 52.3 kW W RIMAX = 42.4 kW W
RIFAULT = 52.3 kW W RIMAX = 42.4 kW W
IOUT IOUT (RLOAD = 5 W) 0A
Figure 7
ON-STATE RESISTANCE vs OUTPUT CURRENT 110 RDS(on) On-State Resistance - m9 -9 RDS(on) On-State Resistance - m9 -9 115 105 95 85 75 65 55
Figure 8
ON-STATE RESISTANCE vs TEMPERATURE
125
VIN = 3 V, I = 1 A 100 VIN = 5 V, I = 1 A 90 Average 80 70 VIN = 5 V, I = 4 A 60 50 40 VIN = 3 V, I = 4 A - 40 0 40 80 120
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
IOUT - Output Current - A
TA - Free-Air Temperature - _C -
Figure 9
Figure 10
8
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UCC3918 LOW ON-RESISTANCE HOT SWAP POWER MANAGER
SLUS384B -- NOVEMBER 1999 -- REVISED JUNE 2000
APPLICATION INFORMATION safety considerations
Although the UCC3918 is designed to provide system protection for all fault conditions, all integrated circuits can ultimately fail short. For this reason, if the UCC3918 is intended for use in safety critical applications where ULO 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 UCC3918 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 Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue 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 party's products or services does not constitute TI's approval, warranty or endorsement thereof.
Copyright (c) 2000, Texas Instruments Incorporated

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