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MAX6495ATT+-MAX6496ATA+T-MAX6497ATA+T-MAX6499ATA+
72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET
General DescriptionThe MAX6495–MAX6499 is a family of small, low-current,
overvoltage-protection circuits for high-voltage transient
systems such as those found in automotive and industrial
applications. These devices monitor the input voltage and
control an external nMOSFET switch to isolate the load
at the output during an input overvoltage condition. The
devices operate over a wide supply voltage range from
+5.5V to +72V.
The gate of the nMOSFET is driven high while the
monitored input is below the user-adjustable overvoltage
threshold. An integrated charge-pump circuit provides a
10V gate-to-source voltage to fully enhance the nMOSFET.
When the input voltage exceeds the user-adjusted over-
voltage threshold, the gate of the MOSFET is quickly
pulled low, disconnecting the load from the input. In some
applications, disconnecting the output from the load is not
desirable. In these cases, the protection circuit can be
configured to act as a voltage limiter where the GATE output
saw-tooths to limit the voltage to the load (MAX6495/
MAX6496/MAX6499).
The MAX6496 supports lower input voltages and reduces
power loss by replacing the external reverse battery diode
with an external series pMOSFET. The MAX6496 generates
the proper bias voltage to ensure that the pMOSFET is
on during normal operations. The gate-to-source voltage is
clamped during load-dump conditions, and the pMOSFET is
off during reverse-battery conditions.
The MAX6497/MAX6498 feature an open-drain, undedicated
comparator that notifies the system if the output falls
below the programmed threshold. The MAX6497 keeps
the MOSFET switch latched off until either the input power
or the SHDN pin is cycled. The MAX6498 will autoretry
when VOVSET falls below 130mV.
These devices are available in small, thermally enhanced,
6-pin and 8-pin TDFN packages and are fully specified
from -40°C to +125°C.
Beneits and Features●Integration and Small Package Saves Board Space
While Ensuring Reliable System Operation3mm x 3mm TDFN PackageSupply Voltage Range: +5.5V to +72VFast Gate Shutoff During Overvoltage with 100mA
Sink CapabilityInternal Charge-Pump Circuit Ensures 10V Gate-to-
Source Enhancement for Low RDS(ON) PerformanceSupports Series pMOSFET for Reverse-Battery
Voltage Protection (MAX6496)POK Indicator (MAX6497/MAX6498)Adjustable Overvoltage ThresholdAdjustable Undervoltage Threshold (MAX6499)●Integrated Protection Features and Wide emperature Range Improve ReliabilityOvervoltage-Protection Switch Controller Allows
User to Size External nMOSFETsnMOSFET Latches Off After an Overvoltage Condition
(MAX6497/MAX6499)Thermal-Shutdown Protection-40°C to +125°C Operating Temperature Range
Applications●Automotive●Industrial●Telecom/Servers/Networking●FireWire®●Notebook Computers
FireWire is a registered trademark of Apple, Inc.
Selector Guide and Ordering Information appear at end of
data sheet.
MAX6495–MAX649972V, Overvoltage-Protection
Switches/Limiter Controllers
with an External MOSFET
EVALUATION KIT AVAILABLE
IN, GATE, GATEP .................................................-0.3V to +80V
SHDN, CLEAR ...........................................-0.3V to (VIN + 0.3V)
POK, OUTFB .........................................................-0.3V to +80V
GATE to OUTFB ....................................................-0.3V to +12V
GATEP to IN ..........................................................-12V to +0.3V
OVSET, UVSET, POKSET ....................................-0.3V to +12V
Current Sink/Source (All Pins) ...........................................50mA
All Other Pins to GND ................................-0.3V to (VIN + 0.3V)
Continuous Power Dissipation (TA = +70°C)
6-Pin TDFN (derate 18.2mW/°C above +70°C) ........1455mW
8-Pin TDFN (derate 18.2mW/°C above +70°C) ........1455mW
Operating Temperature Range .........................-40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range ............................-60°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+260°C
(All pins referenced to GND.)
(VIN = 14V, CGATE = 6nF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSSupply Voltage RangeVIN5.572.0V
Input Supply CurrentIINNo load
SHDN = high 100150SHDN = low (MAX6497/MAX6498/
MAX6499)1524
SHDN = low (MAX6495/MAX6496)2432
IN Undervoltage Lockout VIN rising, enables GATE 4.7555.25V
IN Undervoltage Lockout
Hysteresis VIN falling, disables GATE 155mV
OVSET Threshold Voltage
(MAX6495/MAX6496)
VTH+OVSET rising1.221.241.26VVTH-OVSET falling1.18
OVSET Threshold Hysteresis
(MAX6495/MAX6496)VHYSTOVSET falling5%
OVSET Threshold Voltage
(MAX6497/MAX6498)
VTH+OVSET rising0.4940.5050.518VVTH-OVSET falling0.13
OVSET Threshold Voltage
(MAX6499)
VTH+OVSET rising1.221.241.26VVTH-OVSET falling1.18
UVSET Threshold Voltage
(MAX6499)
VTH+UVSET rising1.221.241.26VVTH-UVSET falling1.18
OVSET/UVSET Threshold
Hysteresis (MAX6499)VHYSTOVSET falling5%
POKSET Threshold Voltage
(MAX6497/MAX6498)
VPOKSET+POKSET rising1.221.241.26VVPOKSET-POKSET falling1.18
POKSET Threshold
Hysteresis (MAX6497/
MAX6498)
VHYSTPOKSET falling5%
OVSET, UVSET, POKSET
Input CurrentISET-50+50nA
Startup Response TimetSTARTSHDN rising (Note 2)100µs
GATE Rise TimeGATE rising from GND to VOUTFB + 8V,
OUTFB = GND1ms
MAX6495–MAX649972V, Overvoltage-Protection
Switches/Limiter Controllers
with an External MOSFET
Absolute Maximum RatingsStresses 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
(VIN = 14V, CGATE = 6nF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
Note 1: Specifications to TA = -40°C are guaranteed by design and not production tested.
Note 2: The MAX6495–MAX6499 power up with the external MOSFET in off mode (VGATE = GND). The external MOSFET turns on
tSTART after all input conditions are valid.
Note 3: For accurate overtemperature-shutdown performance, place the device in close thermal contact with the external MOSFET.
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSOVSET to GATE Propagation
DelaytOVSET rising from VTH - 100mV to VTH + 100mV0.6µs
UVSET to GATE, POKSET to
POK Propagation Delay
POKSET, UVSET falling from VTH + 100mV to
VTH - 100mV20µs
GATE Output High Voltage VOHVOUTFB = VIN = 5.5V, RGATE to IN = 1MΩVIN + 3.4VIN + 3.8VIN + 4.2VVOUTFB = VIN, VIN ≥ 14V, RGATE to IN = 1MΩVIN + 8VIN + 10VIN + 11
GATE Output Low Voltage VOLGATE sinking 15mA, OUTFB = GND1VVIN = 5.5V, GATE sinking 1mA, OUTFB = GND0.9
GATE Charge-Pump CurrentIGATEGATE = GND100µA
GATE to OUTFB Clamp
VoltageVCLMP1218V
IN to GATEP Output Low
Voltage IGATEP_SINK = 75µA, IGATEP_SOURCE = 1µA7.511.7V
IN to GATEP Clamp VoltageVIN = 24V, IGATEP_SOURCE = 10µA1218V
SHDN, CLEAR Logic-High
Input Voltage VIH1.4SHDN, CLEAR Logic-Low
Input Voltage VIL0.4
SHDN Input Pulse Width7µs
CLEAR Input Pulse Width0.5µs
SHDN, CLEAR Input
Pulldown CurrentSHDN is Internally pulled down to GND0.61.01.4µA
Thermal Shutdown (Note 3)+160°C
Thermal-Shutdown
Hysteresis20°C
POKSET to POK Delay
(MAX6497/MAX6498)35µs
POK Output Low Voltage
(MAX6497/MAX6498)VOLVIN ≥ 14V, POKSET = GND, ISINK = 3.2mA 0.4VVIN ≥ 2.8V, POKSET = GND, ISINK = 100µA0.4
POK Leakage Current
(MAX6497/MAX6498)VPOKSET = 14V100nA
MAX6495–MAX649972V, Overvoltage-Protection
Switches/Limiter Controllers
with an External MOSFET
Electrical Characteristics (continued)
(VIN = +12V, TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATUREMAX6495 toc02
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
SET = GND, GATE ENHANCED
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGEMAX6495 toc03
SUPPLY VOLTAGE (V)
SHUTDOWN SUPPLY CURRENT (µA)554535251575
SET = GND, SHDN = GND
MAX6496
GATE VOLTAGE vs. SUPPLY VOLTAGEMAX6495 toc04
SUPPLY VOLTAGE (V)
GATE
- V
(V)554535251575
SET = GND, IN = OUTFB = SHDN
GATEP VOLTAGE vs. SUPPLY VOLTAGEMAX6495 toc05
SUPPLY VOLTAGE (V)
- V
GATEP
(V)554535251575
SET = GND, IN = OUTFB = SHDN
UVLO THRESHOLD vs. TEMPERATUREMAX6495 toc06
TEMPERATURE (°C)
UVLO THRESHOLD (V)
SET = GND, IN = OUTFB = SHDN
FALLING
RISING
SET THRESHOLD vs. TEMPERATUREMAX6495 toc07
SET THRESHOLD (V)
IN = SHDN
FALLING
RISING
SUPPLY CURRENT
vs. SUPPLY VOLTAGEMAX6495 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)5545352515
SET = GND, GATE ENHANCED
GATE TO OUTFB CLAMP VOLTAGE
vs. TEMPERATUREMAX6495 toc08
GATE
- V
OUTFB
(V)
SET = OUTFB = GND
IN = SHDN
MAX6495–MAX649972V, Overvoltage-Protection
Switches/Limiter Controllers
with an External MOSFET
Typical Operating Characteristics
(VIN = +12V, TA = +25°C, unless otherwise noted.)
STARTUP WAVEFORM
(CIN = 100µF, COUT = 10µF, ROUT = 100Ω)MAX6495 toc09
400µs/div
VIN
10V/div
VGATE
10V/div
VOUT
10V/div
STARTUP FROM SHUTDOWN
(CIN = 100µF, COUT = 10µF, ROUT = 100Ω)MAX6495 toc10
400µs/div
VSHDN
1V/div
VGATE
10V/div
VOUT
10V/div
OVERVOLTAGE SWITCH FAULT
(CIN = 100µF, COUT = 10µF, ROUT = 100Ω)MAX6495 toc11
200µs/div
VIN
20V/div
VGATE
20V/div
VOUT
20V/div
OVERVOLTAGE LIMITER
(CIN = 100µF, COUT = 10µF, ROUT = 100Ω)MAX6495 toc12
400µs/div
VIN
20V/div
VGATE
20V/div
VOUT
20V/div
TRIP THRESHOLD = 28V
MAX6495–MAX649972V, Overvoltage-Protection
Switches/Limiter Controllers
with an External MOSFET
Typical Operating Characteristics (continued)
MAX6495–MAX649972V, Overvoltage-Protection
Switches/Limiter Controllers
with an External MOSFET3465
N.C.GATEGND
MAX6496OUTFBOVSETGATEPSHDN
3mm x 3mm TDFNTOP VIEW3465
POKSETGATEGND
MAX6497
MAX6498OUTFBOVSETPOKSHDN
3mm x 3mm TDFN3465
UVSETGATEGND
MAX6499OUTFBOVSETCLEARSHDN
3mm x 3mm TDFN2354SHDNOVSET
OUTFBGATEGND
MAX6495
3mm x 3mm TDFN
Pin Conigurations
PIN
NAMEFUNCTIONMAX6495MAX6496MAX6497/
MAX6498MAX6499111INPositive Supply Voltage. Connect IN to the positive side of the input
voltage. Bypass IN with a 10µF capacitor to GND.222SHDN
Shutdown Input. Drive SHDN low to force GATE low and turn off
the external nMOSFET. Drive SHDN low and then high to reset the
overvoltage-condition latch. SHDN is internally pulled to GND with 1µA
of current. Connect SHDN to IN for normal operation.333OVSET
Overvoltage-Threshold Adjustment Input. Connect OVSET to an
external resistive voltage-divider network to adjust the desired
overvoltage-disable or overvoltage-limit threshold. Connect the resistor
network to the input side (drain) of the nMOSFET for overvoltage switch
turn-off applications or to the output side (source) of the nMOSFET for
overvoltage-limiting applications (MAX6495/MAX6496/MAX6499).555GNDGround666GATE
Gate-Driver Output. Connect GATE to the gate of the external
n-channel MOSFET switch. GATE is the output of a charge pump with
a 100µA pullup current to 10V (typ) above IN during normal operation.
GATE is quickly clamped to OUTFB during an overvoltage condition.
GATE pulls low when SHDN is low.777OUTFBOutput-Voltage-Sense Input. Connect OUTFB to the source of the
external nMOSFET switch.4——GATEP
p-Channel Gate-Driver Output. Connect GATEP to the gate of an external
pMOSFET to provide low-drop reverse-voltage protection. GATEP is
biased to ensure that the pMOSFET is on during normal operating modes,
the gate-to-source is not overstressed during load-dump/overvoltage
conditions, and the pMOSFET is off during reverse-battery conditions.8——N.C.No Connection. Not internally connected.—4—POK
Power-OK Output. POK is an open-drain output. POK remains low
while POKSET is below the internal POKSET threshold. POK goes high
impedance when POKSET goes above the internal POKSET threshold.
Connect POK to an external pullup resistor.—8—
Power-OK Threshold-Adjustment Input. POK remains low while
POKSET is below the internal POKSET threshold (1.18V). POK goes
high impedance when POKSET goes above the internal POKSET
threshold (1.24V). Connect a resistive divider from OUTFB to POKSET
to adjust the desired undervoltage threshold.——4CLEAR
Latch Clear Input. Connect CLEAR to a logic-high to latch the device off after an
overvoltage condition. With OVSET below VTH, pulse CLEAR low (5µs typ) to
reset the output latch. Connect CLEAR to GND to make the latch transparent.——8UVSETUndervoltage-Threshold Adjustment Input. Connect UVSET to an external
resistive voltage-divider network to adjust the desired undervoltage threshold.———EP
Exposed Pad. EP is internally connected to GND. Connect EP to the
ground plane to provide a low thermal-resistance path from the IC junction
to the PC board. Do not use as the primary electrical connection to GND.
MAX6495–MAX649972V, Overvoltage-Protection
Switches/Limiter Controllers
with an External MOSFET
Pin Descriptions
Detailed Description
Overvoltage MonitoringWhen operating in overvoltage mode, the MAX6495–
MAX6499 feedback path (Figure 1) consists of IN,
OVSET’s internal comparator, the internal gate charge
pump, and the external nMOSFET, resulting in a switch-
on/off function. When the programmed overvoltage
threshold is tripped, the internal fast comparator turns off
the external MOSFET, clamping GATE to OUTFB within 0.5μs and disconnecting the power source from the load.
When IN decreases below the adjusted overvoltage
threshold, the MAX6495–MAX6499 slowly enhance GATE
above OUTFB, reconnecting the load to the power source.
Overvoltage Limiter (MAX6495/MAX6496/MAX6499)When operating in overvoltage-limiter mode, the
MAX6495/MAX6496/MAX6499 feedback path (Figure 2)
consists of OUTFB, OVSET’s internal comparator, the
internal gate charge pump, and the external n-channel
MOSFET, resulting in the external MOSFET operating as
a voltage regulator.
During normal operation, GATE is enhanced 10V above
OUTFB. The external MOSFET source voltage is monitored
through a resistive divider between OUTFB and OVSET.
When OUTFB rises above the adjusted overvoltage
threshold, an internal comparator sinks the charge-
pump current, discharging the external GATE, regulating
OUTFB at the OVSET overvoltage threshold. OUTFB
remains active during the overvoltage transients and the
MOSFET continues to conduct during the overvoltage
event, operating in switched-linear mode.
As the transient begins decreasing, OUTFB fall time
will depend on the MOSFET’s GATE charge, the internal
charge-pump current, the output load, and the tank
capacitor at OUTFB.
For fast-rising transients and very large-sized MOSFETs,
add an additional bypass capacitor from GATE to GND
to reduce the effect of the fast-rising voltages at IN.
The external capacitor acts as a voltage-divider working
against the MOSFET’s drain-to-gate capacitance. For a 6000pF gate-to-source capacitance, a 0.1μF capacitor at
GATE will reduce the impact of the fast-rising VIN input.
Caution must be exercised when operating the MAX6495/
MAX6496/MAX6499 in voltage-limiting mode for long
durations. If the VIN is a DC voltage greater than the
MOSFET’s maximum gate voltage, the MOSFET dissi-
pates power continuously. To prevent damage to the exter-
GATE VoltageThe MAX6495–MAX6499 use a high-efficiency charge
pump to generate the GATE voltage. Upon VIN exceed-
ing the 5V (typ) UVLO threshold, GATE enhances 10V
above VIN (for VIN ≥ 14V) with a 100μA pullup current. An
overvoltage condition occurs when the voltage at OVSET
goes above its VTH+ threshold. When the threshold is crossed, GATE falls to OUTFB within 0.5μs with a 100mA
pulldown current. The MAX6495–MAX6499 include an
internal clamp to OUTFB that ensures GATE is limited to
18V (max) above OUTFB to prevent gate-to-source dam-
age of the external MOSFET.
Figure 1. Overvoltage Threshold (MAX6495–MAX6499)
Figure 2. Overvoltage-Limiter Protection Switch Configuration
OVSET
GND
GATEOUTFB
VINVOUT
MAX6495–
MAX6499OVSET
GND
GATEOUTFB
COUT
VINVOUT
MAX6495
MAX6496
MAX6499MAX6495–MAX649972V, Overvoltage-Protection
Switches/Limiter Controllers
with an External MOSFET
