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19-4964; Rev 0; 9/09
Ideal Diode, Reverse-Battery, and Overvoltage Protection Switch/Limiter Controllers with External MOSFETs
General Description
The MAX16914/MAX16915 low-quiescent-current overvoltage and reverse-battery protection controllers are designed for automotive and industrial systems that must tolerate high-voltage transient and fault conditions. These conditions include load dumps, voltage dips, and reversed input voltages. The controllers monitor the input voltage on the supply line and control two external pFETs to isolate the load from the fault condition. The external pFETs are turned on when the input supply exceeds 4.5V and stay on up to the programmed overvoltage threshold. During high-voltage fault conditions, the controllers regulate the output voltage to the set upper threshold voltage (MAX16915), or switch to high resistance (MAX16914) for the duration of the overvoltage transient to prevent damage to the downstream circuitry. The overvoltage event is indicated through an active-low, open-drain output, OV. The reverse-battery pFET behaves as an ideal diode, minimizing the voltage drop when forward biased. Under reverse bias conditions, the pFET is turned off, preventing a downstream tank capacitor from being discharged into the source. Shutdown control turns off the IC completely, disconnecting the input from the output and disconnecting TERM from its external resistor-divider to reduce the quiescent current to a minimum. Both devices are available in a 10-pin FMAXM package and operate over the automotive -40NC to +125NC temperature range. S 4.5V to 19V Input Voltage Operation S Transient Voltage Protection Up to +44V and -75V S Adjustable Overvoltage Limit with ResistorDivider Shut Off in Shutdown S Ideal Diode Reverse-Battery Protection S Low Voltage Drop When Used with Properly Sized External pFETs S Back-Charge Prevention S Overvoltage Indicator S Shutdown Input S 29A Low Operating Current S 6A Low Shutdown Current S Thermal-Overload Protection S -40NC to +125NC Operating Temperature Range S Small 10-Pin MAX Package S AEC-Q100 Qualified
Features
MAX16914/MAX16915
Ordering Information
PART MAX16914AUB/V+ MAX16915AUB/V+ TEMP RANGE -40NC to +125NC -40NC to +125NC PIN-PACKAGE 10 FMAX 10 FMAX
+Denotes a lead(Pb)-free/RoHS-compliant package. /V denotes an automotive qualified device.
Typical Operating Circuit
VBATT P1 P2 VOUT
Applications
Automotive Industrial
Pin Configuration
VCC
TOP VIEW +
VCC 1 GATE1 SENSE IN SHDN OV 2 3 4 5 10 GATE2 9 8 7 6 SENSE OUT TERM SET GND
OFF ON SHDN GATE1 SENSE IN
MAX16914 MAX16915
GATE2
SENSE OUT OV TERM R1 SET R2 OV
MAX16914 MAX16915
GND
MAX is a registered trademark of Maxim Integrated Products, Inc.
_______________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Ideal Diode, Reverse-Battery, and Overvoltage Protection Switch/Limiter Controllers with External MOSFETs MAX16914/MAX16915
ABSOLUTE MAXIMUM RATINGS
VCC, SENSE OUT, TERM, SHDN, OV to GND for P 400ms .............................................................-0.3V to +44V VCC, SENSE OUT, TERM, SHDN, OV to GND for P 90s.............................................................-0.3V to +28V VCC, SENSE OUT, TERM, SHDN, OV to GND .....-0.3V to +20V SENSE IN to GND for P 2ms ..................................-75V to +44V SENSE IN to GND for P 90s ..................................-18V to +44V SENSE IN to GND .................................................-0.3V to +20V GATE1, GATE2 to VCC ..........................................-16V to +0.3V GATE1, GATE2 to GND ........................... -0.3V to (VCC + 0.3V) SET to GND .............................................................-0.3V to +8V Continuous Power Dissipation (TA = +70NC) 10-Pin FMAX (derate 8.8mW/NC above TA = +70NC) (Note 1) .......................................................................707mW Operating Temperature Range ........................ -40NC to +125NC Junction Temperature .....................................................+150NC Storage Temperature Range............................ -65NC to +150NC Lead Temperature (soldering, 10s) ................................+300NC
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
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 in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
PARAMETER Operating Voltage Range Shutdown Supply Current (ISENSE IN + ISENSE OUT + IOV + ISHDN + IVCC) SYMBOL VCC
(VCC = 14V, CGATE1 = 32nF, CGATE2 = 32nF, SHDN = high, TA = -40NC to +125NC, unless otherwise noted. Typical values are at TA = +25NC.) (Note 2)
CONDITIONS (Note 3) TA = +25NC ISHDN SHDN = low, VSENSE OUT = 0V, VTERM = 0V TA = +85NC (Note 3) TA = +125NC (Note 3) TA = +25NC Quiescent Supply Current (ISENSE IN + ISENSE OUT + IOV + ISHDN + IVCC) VCC Undervoltage Lockout VCC Undervoltage-Lockout Hysteresis SET Threshold Voltage SET Threshold Voltage Hysteresis SET Input Current SHDN Low Threshold SHDN High Threshold SHDN Pulldown Current VCC to GATE Output Low Voltage VCC to GATE Clamp Voltage VSETTH VSETHY ISET VSHDNL VSHDNH ISHDN VGVCC1 VGVCC2 VSHDN = 14V, internally pulled to GND VCC = 14V VCC = 42V 6.25 1.4 0.5 7.5 1.0 8.5 14 VSET = 1V VSET rising -3% IQ SHDN = high TA = +85NC (Note 3) TA = +125NC (Note 3) VUVLO VCC rising, VSET = 1V , SHDN = high MIN 4.5 6.0 6.1 6.2 29 30 31 4.06 8 +1.20 4 0.02 0.2 0.4 +3% TYP MAX 19 12 12 12 53 55 57 4.35 V % V % FA V V FA V V FA FA UNITS V
2
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Ideal Diode, Reverse-Battery, and Overvoltage Protection Switch/Limiter Controllers with External MOSFETs
ELECTRICAL CHARACTERISTICS (continued)
PARAMETER TERM On-Resistance TERM Output Current Back-Charge Voltage Fault Threshold Back-Charge Voltage Threshold Hysteresis Back-Charge Turn-Off Time (GATE1) Back-Charge Recovery Time (GATE1) GATE2 Turn-Off Time GATE2 Turn-On Time Startup Response Time (VSHDN Rising) Startup Response Time (VCC Rising) Reverse-Battery Voltage Turn-Off Time/UVLO Turn-Off Time Thermal-Shutdown Temperature Thermal-Shutdown Hysteresis OV Output Low Voltage OV Open-Drain Leakage Current SENSE IN Input Current SENSE OUT Input Current SET to OV Output Low Propagation Delay VOVBL IOVB ISENSE IN ISENSE OUT tOVBPD ISINK = 600FA VSET = 1.0V VSHDN = 0/14V VSHDN = 0/14V VCC = 9.5V, VSET rising from 1V to 1.5V to VOV falling 1 2 3 tSTART1 tSTART2 tREVERSE SYMBOL RTERM ITERM VBCTH VBCHY
MAX16914/MAX16915
(VCC = 14V, CGATE1 = 32nF, CGATE2 = 32nF, SHDN = high, TA = -40NC to +125NC, unless otherwise noted. Typical values are at TA = +25NC.) (Note 2)
CONDITIONS SHDN = high SHDN = low, VTERM = 0V VSENSE OUT = 14V (Note 4) VSENSE OUT = 14V VCC = 9.5V, VSENSE IN = 9V, VSENSE OUT stepped from 4.9V to 9.5V (Note 5) VCC = 9.5V, VSENSE IN = 9V, VSENSE OUT stepped from 9.5V to 4.9V (Note 6) VCC = 9.5V, VSET rising from 1V to 1.5V (Note 7) VCC = 9.5V, VSET falling from 1.5V to 1V (Note 8) VCC = 9.5V, from VSHDN rising to VGATE_ falling (Note 9) VCC rising from 2V to 4.5V, SHDN = high (Note 10) VCC and VSENSE IN falling from 4.25V to 3.25V, VSENSE OUT = 4.25V (Note 11) 18 25 50 MIN TYP 150 MAX 500 1.0 32 UNITS I FA mV mV
tBC
6
10
Fs
tBCREC
18
30
Fs
3 20 100 0.150 30 +170 20 0.4 1.0 5 5
Fs Fs Fs ms Fs NC NC V FA FA FA Fs
Note 2: All parameters are production tested at TA = +25NC. Limits over the operating temperature range are guaranteed by design and characterization. Note 3: Guaranteed by design and characterization. Note 4: The back-charge voltage, VBC, is defined as the voltage at SENSE OUT minus the voltage at SENSE IN. Note 5: Defined as the time from when VBC exceeds VBCTH (25mV typ) to when VGATE1 exceeds VCC - 3.5V. Note 6: Defined as the time from when VBC falls below VBCTH - 50mV to when VGATE1 falls below VCC - 3.5V. Note 7: Defined as the time from when VSET exceeds VSETTH (1.20V typ) to when VGATE2 exceeds VCC - 3.5V. Note 8: Defined as the time from when VSET falls below VSETTH - 5% (1.14V typ) to when VGATE2 falls below VCC - 3.5V. Note 9: The external pFETs can turn on tSTART after the IC is powered up and all input conditions are valid. Note 10: Defined as the time from when VCC exceeds the undervoltage-lockout threshold (4.3V max) to when VGATE1 and VGATE2 fall below 1V. Note 11: Defined as the time from when VCC falls below VSENSE OUT - 25mV to when VGATE1 reaches VCC - 1.75V.
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Ideal Diode, Reverse-Battery, and Overvoltage Protection Switch/Limiter Controllers with External MOSFETs MAX16914/MAX16915
Typical Operating Characteristics
(VCC = 14V, VSHDN = 14V, MAX16914/MAX16915 Evaluation Kit, TA = +25NC, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX16914 toc01
SUPPLY CURRENT vs. TEMPERATURE
MAX16914 toc02
SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX16914 toc03
30 MAX16914 25 MAX16915 20
40 35 SUPPLY CURRENT (FA) 30 25 MAX16915 20 15 10 TERM = OPEN SHDN = HIGH SET = 0V, VCC = 14V NO LOAD -40 -15 10 35 60 85 TEMPERATURE (NC) MAX16914
10 8 SUPPLY CURRENT (FA) 6 4 MAX16915 2 0 4.5 SHDN = LOW SET = 0V 7.0 9.5 12.0 14.5 SUPPLY VOLTAGE (V) MAX16914
SUPPLY CURRENT (A)
15
10 4.5
TERM = OPEN SHDN = HIGH SET = 0V NO LOAD 7.0 9.5 12.0 14.5 17.0 19.0
110 125
17.0 19.0
SUPPLY VOLTAGE (V)
UVLO THRESHOLD vs. TEMPERATURE
MAX16914 toc04
SET THRESHOLD vs. TEMPERATURE
MAX16914 toc05
POWER-UP RESPONSE
MAX16914 toc06
4.3 4.2 UVLO TRESHOLD (V) 4.1 4.0 3.9 3.8 3.7 3.6 3.5 -40 -15 10 35 60 85 TEMPERATURE (NC) 110 FALLING RISING
1.25 RISING SET THRESHOLD (V) 1.20
VCC
10V/div
VOUT
10V/div
1.15
VGATE1
10V/div
FALLING 1.10 125 -40 -15 10 35 60 85 TEMPERATURE (NC) 110 125 40s/div 22F INPUT AND OUTPUT CAPACITOR, ROUT = 100I, SHDN = HIGH
VGATE2
10V/div
STARTUP FROM SHUTDOWN RESPONSE
MAX16914 toc07
OVERVOLTAGE LIMITER RESPONSE (MAX16915)
MAX16914 toc08
OVERVOLTAGE SWITCH-OFF RESPONSE (MAX16914)
MAX16914 toc09
VSHDN 30V
2V/div 14V
VCC
20V/div
30V 14V
VCC
10V/div
VOUT
10V/div 14V 14V
VOUT
20V/div
20V 14V
VOUT
10V/div
14V 0V 14V 0V
VGATE1
10V/div
VOV
20V/div 0V 14V
VOV
20V/div
VGATE2
10V/div 0V
VGATE2
20V/div
30V 0V
VGATE2
20V/div
20s/div 100F INPUT CAPACITOR, 122F OUTPUT CAPACITOR, ROUT = 100I
400s/div VCC = 14V TO 30V TRIP THRESHOLD = 22V 100F INPUT CAPACITOR, 22F OUTPUT CAPACITOR, ROUT = 100I COV = 10nF
1.0s/div VCC = 14V TO 30V TRIP THRESHOLD = 22V 100F INPUT CAPACITOR, 22F OUTPUT CAPACITOR, ROUT = 100I
4
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Ideal Diode, Reverse-Battery, and Overvoltage Protection Switch/Limiter Controllers with External MOSFETs
Typical Operating Characteristics (continued)
(VCC = 14V, VSHDN = 14V, MAX16914/MAX16915 Evaluation Kit, TA = +25NC, unless otherwise noted.)
MAX16914/MAX16915
BACK-CHARGE RESPONSE
MAX16914 toc10
VCC - VGATE_ vs. INPUT VOLTAGE
MAX16914 toc11
GATE-DRIVE VOLTAGE vs. TEMPERATURE
MAX16914 toc12
15.0 13.5 GATE DRIVE VOLTAGE (V) VCC 12.0 10.5 9.0 7.5 6.0 4.5 3.0 1.5 0 SET = GND SHDN = HIGH GATE2 GATE1
6.6
GATE-DRIVE VOLTAGE (V)
5V
5V/div
6.5
GATE1
VOUT
5V/div 5V
6.4 GATE2 6.3 VCC = 14V SET = GND SHDN = HIGH -40 -15 10 35 60 85 TEMPERATURE (NC) 110 125
VGATE1
5V/div 0V
1.0s/div 2.2F INPUT CAPACITOR, 400I INPUT RESISTOR, 22F OUTPUT CAPACITOR
6.2
4.5 9.0 13.5 18.0 22.5 27.0 31.5 36.0 40.5 44.0 SUPPLY VOLTAGE (V)
Pin Description
PIN 1 2 3 NAME VCC GATE1 SENSE IN FUNCTION Positive Supply Input Voltage. Bypass VCC to GND with a 0.1FF or greater ceramic capacitor. Gate-Driver Output. Connect GATE1 to the gate of an external p-channel FET pass switch to provide low drain-to-source voltage drop, reverse voltage protection, and back-charge prevention. Differential Voltage Sense Input (Input Side of IC). Used with SENSE OUT to provide back-charge prevention when the SENSE IN voltage falls below the SENSE OUT voltage by 25mV. Active-Low Shutdown/Wake Input. Drive SHDN high to turn on the voltage detectors. GATE2 is shorted to VCC when SHDN is low. SHDN is internally pulled to GND through a 0.5FA current sink. Connect SHDN to VCC for always-on operation. Open-Drain Overvoltage Indicator Output. Connect a pullup resistor from OV to a positive supply such as VCC. OV is pulled low when the voltage at SET exceeds the internal threshold. Ground Controller Overvoltage Threshold Programming Input. Connect SET to the center of an external resistive divider network between TERM and GND to adjust the desired overvoltage switch-off or limiter threshold. Voltage-Divider Termination Output. TERM is internally connected to SENSE OUT in the MAX16915 and to VCC in the MAX16914. TERM is high impedance when SHDN is low, forcing the current to zero in the resistor-divider connected to TERM. Differential Voltage Sense Input (Output Side Of IC). Used with SENSE IN to provide back-charge prevention when the SENSE IN voltage falls below the SENSE OUT voltage by 25mV. Gate-Driver Output. Connect GATE2 to the gate of an external p-channel FET pass switch. GATE2 is driven low during normal operation and quickly regulated or shorted to VCC during an overvoltage condition. GATE2 is shorted to VCC when SHDN is low.
4
SHDN
5 6 7
OV GND SET
8
TERM
9
SENSE OUT
10
GATE2
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Ideal Diode, Reverse-Battery, and Overvoltage Protection Switch/Limiter Controllers with External MOSFETs MAX16914/MAX16915
Functional Diagram
VCC
REG GATE1
1.20V OV1 GATE2
SENSE IN
SENSE OUT SET TO VCC FOR MAX16914
SHDN
BANDGAP BIAS
TO SENSE OUT FOR MAX16915
OV
TERM SWITCH OV1 TERM
MAX16914 MAX16915
GND
Detailed Description
The MAX16914/MAX16915 are ultra-small, low-quiescent, high load-current, overvoltage-protection circuits for automotive or industrial applications. These devices monitor the input and output voltages and control two p-channel MOSFETs to protect downstream loads from reverse-battery, overvoltage, and high-voltage transient conditions and prevent downstream tank capacitors from discharging into the source (back-charging). One MOSFET (P1) eliminates the need for external diodes, thus minimizing the input voltage drop and provides back-charge and reverse-battery protection. The second MOSFET (P2) isolates the load or regulates the output voltage during an overvoltage condition. These ICs allow system designers to size the external p-channel MOSFET to their load current, voltage drop, and board size.
6
In the MAX16914, the input voltage is monitored (TERM is internally shorted to VCC--see the Functional Diagram) making the device an overvoltage switch-off controller. As the VCC voltage rises, and the programmed overvoltage threshold is tripped, the internal fast comparator turns off the external p-channel MOSFET (P2), pulling GATE2 to VCC to disconnect the power source from the load. When the monitored voltage goes below the adjusted overvoltage threshold, the MAX16914 enhances GATE2, reconnecting the load to the power source.
Overvoltage Switch-Off Controller (MAX16914)
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Ideal Diode, Reverse-Battery, and Overvoltage Protection Switch/Limiter Controllers with External MOSFETs
In the MAX16915, TERM is internally connected to SENSE OUT (see the Functional Diagram) allowing the IC to operate in voltage-limiter mode.
Overvoltage Limiter Controller (MAX16915)
During normal operation, GATE2 is pulled low to fully enhance the MOSFET. The external MOSFET's drain voltage is monitored through a resistor-divider between TERM, SET, and GND. When the output voltage rises above the adjusted overvoltage threshold, an internal comparator pulls GATE2 to VCC turning off P2. When the monitored voltage goes below the overvoltage threshold (-4% hysteresis), the p-channel MOSFET (P2) is turned on again. During a continuous overvoltage condition, MOSFET (P2) cycles on and off (between the overvoltage threshold and the hysteresis), generating a sawtooth waveform with a frequency dependent on the load capacitance and load current. This process continues to keep the voltage at the output regulated to within approximately a 4% window. The output voltage is regulated during the overvoltage transients and MOSFET (P2) continues to conduct during the overvoltage event, operating in switched-linear mode. Caution must be exercised when operating the MAX16915 in voltage-limiting mode for long durations due to the MOSFET's power-dissipation consideration (see the MOSFET Selection section).
The MAX16914/MAX16915 feature an active-low shutdown input (SHDN). Drive SHDN low to switch off FET (P2), disconnecting the input from the output, thus placing the IC in low-quiescent-current mode. Reversebattery protection is still maintained. The MAX16914/MAX16915 feature reverse-battery protection to prevent damage to the downstream circuitry caused by battery reversal or negative transients. The reverse-battery protection blocks the flow of current into the downstream load and allows the circuit designer to remove series-protection diodes. The MAX16914/MAX16915 monitor the input-to-output differential voltage between SENSE IN and SENSE OUT. It turns off the external FET (P1) when (VSENSE OUT VSENSE IN) > 25mV (see Figure 1) to prevent discharging of a downstream tank capacitor into the battery supply during an input voltage drop, such as a cold-crank condition or during a superimposed sinusoidal voltage on top of the supply voltage. It turns on the FET (P1) again if the back-charge voltage threshold hysteresis of 50mV is satisfied.
Shutdown
MAX16914/MAX16915
Reverse-Battery Protection
Back-Charge Switch-Off
tBC = 10s (max) VOUT - VBATT = 50mV
50% (25mV) VOUT - VBATT = 0V
VBATT = 9V
50% IOUT
Figure 1. Back-Charge Turn-Off Time
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7
Ideal Diode, Reverse-Battery, and Overvoltage Protection Switch/Limiter Controllers with External MOSFETs MAX16914/MAX16915
The MAX16914/MAX16915 include an active-low, open-drain overvoltage-indicator output (OV). For the MAX16914, OV asserts low when VCC exceeds the programmed overvoltage threshold. OV deasserts when the overvoltage condition is over. For the MAX16915, OV asserts if VOUT exceeds the programmed overvoltage threshold. OV deasserts when VOUT drops 4% (typ) below the overvoltage threshold level. If the overvoltage condition continues, OV may toggle with the same frequency as the overvoltage limiter FET (P2). If the P2 device is turned on for a very short period (less than tOVBPD), the OV pin may not toggle. To obtain a logic-level output, connect a 45kI pullup resistor from OV to a system voltage less than 44V. A capacitor connected from OV to GND helps extend the time that the logic level remains low.
Overvoltage Indicator Output (OV)
For example: With an overvoltage threshold (VOV) set to 20V, RTOTAL < 20V/(100 x ISET), where ISET = 1FA (max). RTOTAL < 200kI Use the following formula to calculate R2: R2 = (VTH x RTOTAL)/VOV where VTH is the 1.20V SET rising threshold and VOV is the desired overvoltage threshold. Then, R2 = 12.0kI. Use the nearest standard-value resistor lower than the calculated value. A lower value for total resistance dissipates more power but provides slightly better accuracy. To determine R1: RTOTAL = R2 + R1 Then, R1 = 188kI. Use the nearest standard-value resistor lower than the calculated value. A lower value for total resistance dissipates more power but provides slightly better accuracy.
Applications Information
Most automotive applications run off a multicell "12V" lead-acid battery with a nominal voltage that swings between 9V and 16V (depending on load current, charging status, temperature, battery age, etc.). The battery voltage is distributed throughout the automobile and is locally regulated down to voltages required by the different system modules. Load dump occurs when the alternator is charging the battery and the battery becomes disconnected. The alternator voltage regulator is temporarily driven out of control. Power from the alternator flows into the distributed power system and elevates the voltage seen at each module. The voltage spikes have rise times typically greater than 5ms and decays within several hundred milliseconds but can extend out to 1s or more depending on the characteristics of the charging system. These transients are capable of destroying sensitive electronic equipment on the first "fault event." TERM and SET provide an accurate means to set the overvoltage level for the MAX16914/MAX16915. Use a resistive divider to set the desired overvoltage condition (see the Typical Operating Circuit). VSET has a rising 1.20V threshold with a 4% falling hysteresis. Begin by selecting the total end-to-end resistance: RTOTAL = R1 + R2 For high accuracy, choose RTOTAL to yield a total current equivalent to a minimum 100 x ISET where ISET is the input bias current at SET.
Load Dump
MOSFET Selection
Output p-Channel MOSFET (P2) Select the external output MOSFET according to the application current level. The MOSFET's on-resistance (RDS(ON)) should be chosen low enough to have a minimum voltage drop at full load to limit the MOSFET power dissipation. Determine the device power rating to accommodate an overvoltage fault when operating the MAX16915 in overvoltage-limiting mode. During normal operation for either IC, the external MOSFET dissipates little power. The power dissipated in the MOSFET during normal operation is: PNORM = ILOAD2 x RDS(ON) where PNORM is the power dissipated in the MOSFET in normal operation, ILOAD is the output load current, and RDS(ON) is the drain-to-source resistance of the MOSFET. Worst-case power dissipation in the output MOSFET occurs during a prolonged overvoltage event when operating the MAX16915 in voltage-limiting mode. The power dissipated across the MOSFET is as follows: POVLO = VDS x ILOAD where POVLO is the power dissipated in the MOSFET in overvoltage-limiting operation, VDS is the voltage across the MOSFET's drain and source, and ILOAD is the load current.
Setting Overvoltage Thresholds
8
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Ideal Diode, Reverse-Battery, and Overvoltage Protection Switch/Limiter Controllers with External MOSFETs
Reverse-Polarity Protection MOSFET (P1) Most battery-powered applications must include reversevoltage protection. Many times this is implemented with a diode in series with the battery. The disadvantage in using a diode is the forward-voltage drop of the diode, which reduces the operating voltage available to downstream circuits (VLOAD = VBATTERY - VDIODE). The MAX16914/MAX16915 include high-voltage GATE1 drive circuitry allowing users to replace the high-voltage drop series diode with a low-voltage-drop MOSFET device (as shown in the Typical Operating Circuit). The forward-voltage drop is reduced to ILOAD x RDS(ON) of P1. With a suitably chosen MOSFET, the voltage drop can be reduced to millivolts. In normal operating mode, internal GATE1 output circuitry enhances P1. The constant enhancement ensures P1 operates in a low RDS(ON) mode, but the gate-source junction is not overstressed during high battery-voltage applications or transients (many MOSFET devices specify a Q20V VGS absolute maximum). As VCC drops below 10V, GATE1 is limited to GND, reducing P1 VGS to VCC. In normal operation, the P1 power dissipation is very low: P1 = ILOAD2 x RDS(ON) During reverse-battery conditions, GATE1 is limited to GND and the P1 gate-source junction is reverse biased. P1 is turned off and neither the MAX16914/MAX16915 nor the load circuitry is exposed to the reverse-battery voltage. Care should be taken to place P1 (and its internal drain-to-source diode) in the correct orientation for proper reverse-battery operation. The MAX16914/MAX16915 thermal-shutdown feature turns off both MOSFETs if the IC junction temperature exceeds the maximum allowable thermal dissipation. When the junction temperature exceeds TJ = +170NC, the thermal sensor signals the shutdown logic, turning off both GATE1 and GATE2 outputs and allowing the device to cool. The thermal sensor turns GATE1 and GATE2 on again after the IC's junction temperature cools by 20NC. For continuous operation, do not exceed the absolute maximum junction-temperature rating of TJ = +150NC.
MAX16914/MAX16915
Thermal Shutdown
Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 21-0061
10 FMAX
U10+2
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
(c)
9
2009 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.

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