MAX6495ATT+TG128

EVALUATION KIT AVAILABLE Click here for production status of specific part numbers. MAX6495–MAX6499 General Description The 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 overvoltage 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. FireWire is a registered trademark of Apple, Inc. 19-3778; Rev 16; 4/18 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET Benefits and Features ●● Integration and Small Package Saves Board Space While Ensuring Reliable System Operation • 3mm x 3mm TDFN Package • Supply Voltage Range: +5.5V to +72V • Fast Gate Shutoff During Overvoltage with 100mA Sink Capability • Internal Charge-Pump Circuit Ensures 10V Gate-toSource Enhancement for Low RDS(ON) Performance • Supports Series pMOSFET for Reverse-Battery Voltage Protection (MAX6496) • POK Indicator (MAX6497/MAX6498) • Adjustable Overvoltage Threshold • Adjustable Undervoltage Threshold (MAX6499) ●● Integrated Protection Features and Wide Temperature Range Improve Reliability • Overvoltage-Protection Switch Controller Allows User to Size External nMOSFETs • nMOSFET Latches Off After an Overvoltage Condition (MAX6497/MAX6499) • Thermal-Shutdown Protection • -40°C to +125°C Operating Temperature Range • AEC-Q100 Qualified (MAX6495ATT/V+, MAX6496ATA/V+T, and MAX6499ATA/V+ Only) Applications ●● ●● ●● ●● ●● Automotive Industrial Telecom/Servers/Networking FireWire® Notebook Computers Selector Guide and Ordering Information appear at end of data sheet. MAX6495–MAX6499 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET Absolute Maximum Ratings (All pins referenced to GND.) 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 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. Package Information 6 TDFN-EP PACKAGE CODE T633+2 Outline Number 21-0137 Land Pattern Number 90-0058 Thermal Resistance, Single-Layer Board: Junction to Ambient (θJA) 55°C/W Junction to Case (θJC) 9°C/W Thermal Resistance, Four-Layer Board: Junction to Ambient (θJA) 42°C/W Junction to Case (θJC) 9 8 TDFN-EP PACKAGE CODE T833+2 Outline Number 21-0137 Land Pattern Number 90-0058 Thermal Resistance, Single-Layer Board: Junction to Ambient (θJA) 54°C/W Junction to Case (θJC) 8°C/W Thermal Resistance, Four-Layer Board: Junction to Ambient (θJA) 41°C/W Junction to Case (θJC) 8°C/W For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial. www.maximintegrated.com Maxim Integrated │  2 MAX6495–MAX6499 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET Electrical Characteristics (VIN = 14V, CGATE = 6nF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER Supply Voltage Range Input Supply Current SYMBOL CONDITIONS VIN IIN MIN TYP 5.5 No load SHDN = low (MAX6497/MAX6498/ MAX6499) 15 24 IN Undervoltage Lockout Hysteresis VIN falling, disables GATE 4.75 24 32 5 5.25 155 VTH+ OVSET rising VTH- OVSET falling 1.18 VHYST OVSET falling 5 OVSET Threshold Voltage (MAX6497/MAX6498) VTH+ OVSET rising OVSET Threshold Voltage (MAX6499) VTH+ OVSET rising UVSET Threshold Voltage (MAX6499) VTH+ UVSET rising POKSET Threshold Voltage (MAX6497/MAX6498) POKSET Threshold Hysteresis (MAX6497/ MAX6498) OVSET, UVSET, POKSET Input Current Startup Response Time OVSET falling VTH- UVSET falling 1.18 VHYST OVSET falling 5 VPOKSET+ POKSET rising 1.22 tSTART 1.22 POKSET falling VOH GATE Output Low Voltage VOL GATE Charge-Pump Current IGATE GATE to OUTFB Clamp Voltage VCLMP 1.26 1.24 1.26 1.24 1.26 +50 VOUTFB = VIN, VIN ≥ 14V, RGATE to IN = 1MΩ GATE sinking 15mA, OUTFB = GND µs µs VIN + 10 VIN + 11 1 0.9 100 12 nA ms VIN + 3.4 VIN + 3.8 VIN + 4.2 GATE = GND V 1 20 VIN = 5.5V, GATE sinking 1mA, OUTFB = GND V µs 0.6 VIN + 8 V 100 SET rising from VTH - 100mV to VTH + 100mV VOUTFB = VIN = 5.5V, RGATE to IN = 1MΩ V % -50 SHDN rising (Note 2) V % 5 POKSET, UVSET falling from VTH + 100mV to VTH - 100mV GATE Output High Voltage 1.24 1.18 GATE rising from GND to VOUTFB + 8V, OUTFB = GND tOV 0.518 1.18 1.22 V % 0.13 VPOKSET- POKSET falling ISET 1.26 0.505 VTH- UVSET to GATE, POKSET to POK Propagation Delay www.maximintegrated.com 0.494 µA mV 1.24 OVSET falling GATE Rise Time OVSET to GATE Propagation Delay 1.22 VTH- VHYST V 150 SHDN = low (MAX6495/MAX6496) OVSET/UVSET Threshold Hysteresis (MAX6499) 72.0 100 VIN rising, enables GATE OVSET Threshold Hysteresis (MAX6495/MAX6496) UNITS SHDN = high IN Undervoltage Lockout OVSET Threshold Voltage (MAX6495/MAX6496) MAX V V µA 18 V Maxim Integrated │  3 MAX6495–MAX6499 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET Electrical Characteristics (continued) (VIN = 14V, CGATE = 6nF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS IN to GATEP Output Low Voltage IGATEP_SINK = 75µA, IGATEP_SOURCE = 1µA 7.5 11.7 V IN to GATEP Clamp Voltage VIN = 24V, IGATEP_SOURCE = 10µA 12 18 V SHDN, CLEAR Logic-High Input Voltage VIH SHDN, CLEAR Logic-Low Input Voltage VIL 1.4 V 0.4 SHDN Input Pulse Width 7 CLEAR Input Pulse Width µs 0.5 SHDN, CLEAR Input Pulldown Current SHDN is Internally pulled down to GND Thermal Shutdown (Note 3) 0.6 1.0 µs 1.4 µA +160 °C Thermal-Shutdown Hysteresis 20 °C POKSET to POK Delay (MAX6497/MAX6498) 35 µs POK Output Low Voltage (MAX6497/MAX6498) POK Leakage Current (MAX6497/MAX6498) VOL VIN ≥ 14V, POKSET = GND, ISINK = 3.2mA 0.4 VIN ≥ 2.8V, POKSET = GND, ISINK = 100µA 0.4 VPOKSET = 14V 100 V nA 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. www.maximintegrated.com Maxim Integrated │  4 MAX6495–MAX6499 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET Typical Operating Characteristics (VIN = +12V, TA = +25°C, unless otherwise noted.) 60 35 107.5 105.0 102.5 5 15 25 35 45 55 65 100.0 75 GATE VOLTAGE vs. SUPPLY VOLTAGE MAX6495 toc04 12 SET = GND, IN = OUTFB = SHDN 20 5 15 GATEP VOLTAGE vs. SUPPLY VOLTAGE 5.5 SET = GND, IN = OUTFB = SHDN 5.4 35 6 3 5 15 25 35 45 55 65 75 0 SET = GND, IN = OUTFB = SHDN SUPPLY VOLTAGE (V) 45 55 65 5.0 4.9 4.8 FALLING SET THRESHOLD vs. TEMPERATURE IN = SHDN 1.30 75 4.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 16.5 16.4 16.3 VGATE - VOUTFB (V) SET THRESHOLD (V) 35 RISING 1.25 1.20 75 RISING 5.1 SUPPLY VOLTAGE (V) 1.35 GATE TO OUTFB CLAMP VOLTAGE vs. TEMPERATURE SET = OUTFB = GND IN = SHDN 16.2 16.1 16.0 15.9 15.8 15.7 1.15 FALLING 1.10 25 MAX6495 toc07 1.40 15 65 5.2 4.7 5 55 UVLO THRESHOLD vs. TEMPERATURE 4.6 0 45 5.3 UVLO THRESHOLD (V) VIN - VGATEP (V) 3 25 SUPPLY VOLTAGE (V) 9 6 MAX6495 toc03 30 TEMPERATURE (°C) 9 VGATE - VIN (V) 40 10 -40 -25 -10 5 20 35 50 65 80 95 110 125 SUPPLY VOLTAGE (V) 12 MAX6495 toc02 110.0 MAX6495 toc05 10 112.5 SET = GND, SHDN = GND MAX6496 MAX6495 toc06 85 115.0 SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE 50 SHUTDOWN SUPPLY CURRENT (µA) 110 SET = GND, GATE ENHANCED 117.5 SUPPLY CURRENT (µA) SUPPLY CURRENT (µA) 135 120.0 MAX6495 toc01 SET = GND, GATE ENHANCED SUPPLY CURRENT vs. TEMPERATURE MAX6495 toc08 SUPPLY CURRENT vs. SUPPLY VOLTAGE -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) www.maximintegrated.com 15.6 15.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) Maxim Integrated │  5 MAX6495–MAX6499 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET Typical Operating Characteristics (continued) (VIN = +12V, TA = +25°C, unless otherwise noted.) STARTUP WAVEFORM (CIN = 100µF, COUT = 10µF, ROUT = 100Ω) STARTUP FROM SHUTDOWN (CIN = 100µF, COUT = 10µF, ROUT = 100Ω) MAX6495 toc09 MAX6495 toc10 VIN 10V/div VSHDN 1V/div VGATE 10V/div VGATE 10V/div VOUT 10V/div VOUT 10V/div 400µs/div 400µs/div OVERVOLTAGE SWITCH FAULT (CIN = 100µF, COUT = 10µF, ROUT = 100Ω) OVERVOLTAGE LIMITER (CIN = 100µF, COUT = 10µF, ROUT = 100Ω) MAX6495 toc11 MAX6495 toc12 VIN 20V/div VIN 20V/div VGATE 20V/div VGATE 20V/div VOUT 20V/div 200µs/div www.maximintegrated.com VOUT 20V/div TRIP THRESHOLD = 28V 400µs/div Maxim Integrated │  6 MAX6495–MAX6499 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET Pin Configurations TOP VIEW N.C. OUTFB GATE GND 8 7 6 5 POKSET OUTFB GATE GND 8 7 1 2 3 4 SHDN OVSET GATEP 3mm x 3mm TDFN UVSET OUTFB GATE GND 8 7 6 5 1 2 IN 1 2 3 4 3mm x 3mm TDFN OUTFB GATE 6 GND 5 4 MAX6495 4 SHDN OVSETCLEAR 3mm x 3mm TDFN www.maximintegrated.com 3 SHDN OVSET POK MAX6499 IN 5 MAX6497 MAX6498 MAX6496 IN 6 1 2 3 IN SHDN OVSET 3mm x 3mm TDFN Maxim Integrated │  7 MAX6495–MAX6499 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET Pin Descriptions PIN MAX6495 MAX6496 1 1 2 2 MAX6497/ MAX6499 MAX6498 1 2 1 2 NAME IN SHDN FUNCTION Positive Supply Voltage. Connect IN to the positive side of the input voltage. Bypass IN with a 10µF capacitor to GND. 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. 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). Ground 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. 3 3 3 3 OVSET 4 5 5 5 GND 5 6 6 6 GATE 6 7 7 7 OUTFB Output-Voltage-Sense Input. Connect OUTFB to the source of the external nMOSFET switch. 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 loaddump/overvoltage conditions, and the pMOSFET is off during reversebattery conditions. — 4 — — GATEP — 8 — — N.C. No Connection. Not internally connected. 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. — — — — 4 8 — — Power-OK Threshold-Adjustment Input. POK remains low while POKSET is below the internal POKSET threshold (1.18V). POK goes POKSET 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. — — — 4 CLEAR 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. — — — 8 UVSET Undervoltage-Threshold Adjustment Input. Connect UVSET to an external resistive voltage-divider network to adjust the desired undervoltage threshold. — — www.maximintegrated.com — — 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. Maxim Integrated │  8 MAX6495–MAX6499 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET Detailed Description When 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 switchon/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 chargepump 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 dissipates power continuously. To prevent damage to the external MOSFET, proper heatsinking should be implemented. www.maximintegrated.com VOUT VIN Overvoltage Monitoring GATE IN OUTFB MAX6495– MAX6499 R1 OVSET R2 GND Figure 1. Overvoltage Threshold (MAX6495–MAX6499) VOUT VIN COUT GATE IN OUTFB MAX6495 MAX6496 MAX6499 R1 OVSET GND R2 Figure 2. Overvoltage-Limiter Protection Switch Configuration GATE Voltage The MAX6495–MAX6499 use a high-efficiency charge pump to generate the GATE voltage. Upon VIN exceeding 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 damage of the external MOSFET. Maxim Integrated │  9 MAX6495–MAX6499 The gate cycles during overvoltage-limit and overvoltageswitch modes are quite similar but have distinct characteristics. In overvoltage-switch mode, GATE is enhanced to (VIN + 10V) while the monitored VIN voltage remains below the overvoltage fault threshold (OVSET < VTH+). When an overvoltage fault occurs (OVSET ≥ VTH+), GATE is pulled one diode drop below OUTFB, turning off the external MOSFET and disconnecting the load from the input. GATE remains low (MOSFET off) as long as the VIN voltage is above the overvoltage fault threshold. As VIN falls back below the overvoltage fault threshold, GATE is again enhanced to (VIN + 10V). 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET R  V TRIPLOW = (VTH− )  TOTAL   R2 + R3  R  V TRIPHIGH = (V TH+ )  TOTAL   R3  where RTOTAL = R1 + R2 + R3. Use the following steps to determine the values for R1, R2, and R3: 1) Choose a value for RTOTAL, the sum of R1, R2, and R3. Because the MAX6499 has very high input impedance, RTOTAL can be up to 5MΩ. In overvoltage-limit mode, GATE is enhanced to (VIN 2) Calculate R3 based on RTOTAL and the desired upper +10V) while the monitored OUTFB voltage remains below trip point: the overvoltage fault threshold (OVSET < VTH+). When an overvoltage fault occurs (OVSET ≥ VTH+), GATE is V × R TOTAL R3 = TH+ pulled one diode drop below OUTFB until OUTFB drops V TRIPHIGH 5% below the overvoltage fault threshold (MAX6495/ MAX6496/MAX6499). GATE is then turned back on until 3) Calculate R2 based on RTOTAL, R3, and the desired OUTFB reaches the overvoltage fault threshold and lower trip point: GATE is again turned off. GATE cycles in a saw-tooth ( V waveform until OUTFB remains below the overvoltage ) × R TOTAL  − R3 = R2  TH−  fault threshold and GATE remains constantly on (VIN  V TRIPLOW  +10V). The overvoltage limiter’s sawtooth GATE output 4) Calculate R1 based on RTOTAL, R2, and R3: operates the MOSFET in a switched-linear mode while the input voltage remains above the overvoltage fault R1 = RTOTAL – R2 – R3 threshold. The sawtooth frequency depends on the load To improve ESD protection, keep R3 ≥ 1kΩ. capacitance, load current, and MOSFET turn-on time (GATE charge current and GATE capacitance). GATE goes high when the following startup conditions are met: VIN is above the UVLO threshold, SHDN is high, an overvoltage fault is not present, and the device is not in thermal shutdown. DC-DC CONVERTER IN VIN Undervoltage Monitoring (MAX6499) The MAX6499 includes undervoltage and overvoltage comparators for window detection (see Figure 3 and Figure 12). GATE is enhanced and the nMOSFET is on when the monitored voltage is within the selected “window.” When the monitored voltage falls below the lower limit (VTRIPLOW) or exceeds the upper limit (VTRIPHIGH) of the window, GATE falls to OUTFB turning off the MOSFET. The application in Figure 3 shows the MAX6499 enabling the DC-DC converter when the monitored voltage is in the selected window. The resistor values R1, R2, and R3 can be calculated as follows: www.maximintegrated.com GATE OUTFB IN R1 OUT GND SHDN UVSET R2 MAX6499 OVSET R3 CLEAR GND Figure 3. MAX6499 Window-Detector Circuit Maxim Integrated │  10 MAX6495–MAX6499 Power-OK Output (MAX6497/MAX6498) POK is an open-drain output that remains low when the voltage at 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 GND, and the divider center node to POKSET, to adjust the desired undervoltage threshold. Use a resistor in the 100kΩ range from POKSET to GND to minimize current consumption. Overvoltage Latch Function The MAX6497/MAX6499 offers a latch function that prevents the external MOSFET from turning on until the latch is cleared. For the MAX6497, the latch can be cleared by cycling the power on the input IN to a voltage below the undervoltage lockout or by pulling the shutdown input low and then back to a logic-high state. The MAX6499 offers a CLEAR input that latches the nMOSFET off when CLEAR is high. The latch is removed when the CLEAR input is pulsed low. Connect CLEAR low to make the latch transparent. Overvoltage Retry Function The MAX6498 offers an automatic retry function that tries to enhance the external nMOSFET after the overvoltage condition is removed. When the monitored input voltage detects an overvoltage condition (VSET > VTH+), the nMOSFET is turned off. The MOSFET stays off until the voltage at VSET falls below its VTH- (typically 0.13V), at which point the output tries to turn on again. Applications Information Load Dump 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.” www.maximintegrated.com 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET Setting Overvoltage Thresholds OVSET provides an accurate means to set the overvoltage level for the devices. Use a resistive divider to set the desired overvoltage condition (see Figure 2). OVSET has a rising 1.24V threshold with a 5% falling hysteresis (MAX6495/ MAX6496/MAX6499) and a rising 0.505V threshold with a falling 0.15V threshold (MAX6497/MAX6498). Begin by selecting the total end-to-end resistance, RTOTAL = R1 + R2. Choose RTOTAL to yield a total current equivalent to a minimum 100 x ISET (OVSET’s input bias current) at the desired overvoltage threshold. For example: With an overvoltage threshold (VOV) set to 20V for the MAX6495/MAX6496/MAX6499, RTOTAL < 20V/(100 x ISET), where ISET is OVSET’s 50nA (max) input bias current. RTOTAL < 4MΩ Use the following formula to calculate R2: = R2 V TH+ × R TOTAL VOV where VTH+ is the 1.24V OVSET rising threshold and VOV is the desired overvoltage threshold. R2 = 248kΩ. Use a 249kΩ standard resistor. RTOTAL = R2 + R1, where R1 = 3.751MΩ. Use a 3.74MΩ standard resistor. A lower value for total resistance dissipates more power but provides slightly better accuracy. To improve ESD protection, keep R2 ≥ 1kΩ. Reverse-Battery Protection The MAX6496 is an overvoltage-protection circuit that is capable of driving a pMOSFET to prevent reverse-battery conditions. This MOSFET eliminates the need for external diodes, thus minimizing the input voltage drop (see Figure 8). Inrush/Slew-Rate Control Inrush current control can be implemented by placing a capacitor from GATE to GND to slowly ramp up the GATE, thus limiting the inrush current and controlling GATE’s slew rate during initial turn-on. The inrush current can be approximated using the following equation: IINRUSH = C OUT × I GATE + ILOAD C GATE where IGATE is GATE’s 100μA sourcing current, ILOAD is the load current at startup, and COUT is the output capacitor. Maxim Integrated │  11 MAX6495–MAX6499 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET MOSFET Selection Peak Power-Dissipation Limit During normal operation, the external MOSFET dissipates little power. The power dissipated in the MOSFET during normal operation is: Depending on the output capacitance and the initial voltage, a significant amount of energy may be dissipated by the internal 100mA pulldown. To prevent damage to the device ensure that for a given overvoltage threshold, the output capacitance does not exceed the limit provided in Figure 4. This output capacitance represents the sum of all capacitors connected to OUTFB, including reservoir capacitors and DC-DC input filter capacitors. Select external MOSFETs 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 MAX6495/MAX6496/MAX6499 in overvoltage-limit mode. P = ILOAD2 x RDS(ON) where P is the power dissipated in the MOSFET, ILOAD is the output load current, and RDS(ON) is the drain-tosource resistance of the MOSFET. Most power dissipation in the MOSFET occurs during a prolonged overvoltage event when operating the MAX6495/MAX6496/MAX6499 in voltage-limiter mode. The power dissipated across the MOSFET is as follows (see the Thermal Shutdown in Overvoltage-Limiter Mode section): P = VDS x ILOAD The devices activate an internal 100mA pulldown on GATE when SHDN goes low, OVSET exceeds its threshold or UVSET falls below its threshold. Once the voltage on GATE falls below the OUTFB voltage, current begins to flow from OUTFB to the 100mA pulldown through the internal clamp diode, discharging the output capacitors. Thermal Shutdown in Overvoltage-Limiter Mode When operating the MAX6495/MAX6496/MAX6499 in overvoltage-limit mode for a prolonged period of time, a thermal shutdown is possible. The thermal shutdown is dependent on a number of different factors: ●● The device’s ambient temperature where VDS is the voltage across the MOSFET’s drain and source. ●● The output capacitor (COUT) Thermal Shutdown ●● The overvoltage threshold limit (VOV) ●● The overvoltage waveform period (tOV) When the junction temperature exceeds TJ = +160°C, the thermal sensor signals the shutdown logic, turning off the GATE output and allowing the device to cool. The thermal sensor turns the GATE on again after the IC’s junction temperature cools by 20°C. Thermal-overload protection is designed to protect the MAX6495–MAX6499 and the external MOSFET in the event of current-limit fault conditions. For continuous operation, do not exceed the absolute maximum junction temperature rating of TJ = +150°C. ●● The power dissipated across the package (PDISS) MAXIMUM OUTPUT CAPACITANCE vs. OVERVOLTAGE THRESHOLD MAX6495 fig04 100,000 MAXIMUM OUTPUT CAPACITANCE (µF) The devices’ thermal-shutdown feature turns off GATE if it exceeds the maximum allowable thermal dissipation. Thermal shutdown also monitors the PC board temperature of the external nMOSFET when the devices sit on the same thermal island. Good thermal contact between the MAX6495–MAX6499 and the external nMOSFET is essential for the thermal-shutdown feature to operate effectively. Place the nMOSFET as close to possible to OUTFB. ●● The output load current (IOUT) 10,000 1000 SAFE OPERATING AREA 100 10 0 10 20 30 40 50 60 70 OVERVOLTAGE THRESHOLD (V) Figure 4. Safe Operating Area for 100mA Pulldown www.maximintegrated.com Maxim Integrated │  12 MAX6495–MAX6499 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET During an initial overvoltage occurrence, the discharge time (Δt1) of COUT, caused by IOUT and IGATEPD. The discharge time is approximately: ∆t 1 = C OUT VOV × 0.05 (I OUT + I GATEPD ) where VOV is the overvoltage threshold, IOUT is the load current, and IGATEPD is the GATE’s 100mA pulldown current. Upon OUT falling below the threshold point, the MAX6495/ MAX6496/MAX6499s’ charge-pump current must recover and begins recharging the external GATE voltage. The time needed to recharge GATE from -VD to the MOSFET’s gate threshold voltage is: ∆t 2 = C ISS VGS(TH) + VD I GATE where CISS is the MOSFET’s input capacitance, VGS(TH) is the MOSFET’s gate threshold voltage, VD is the internal clamp (from OUTFB to GATE) diode’s forward voltage (1.5V, typ) and IGATE is the charge-pump current (100μA typ). During Δt2, COUT loses charge through the output load. The voltage across COUT (ΔV2) decreases until the MOSFET reaches its VGS(TH) threshold and can be approximated using the following formula: ∆V 2 = I OUT GATE OUTFB ∆t 2 C OUT t2 t1 t3 tOV Once the MOSFET VGS(TH) is obtained, the slope of the output-voltage rise is determined by the MOSFET Qg charge through the internal charge pump with respect to the drain potential. The new rise time needed to reach a new overvoltage event can be calculated using the following formula: ∆t 3 ≅ Q GD ∆VOUT VGS I GATE where QGD is the gate-to-drain charge. The total period of the overvoltage waveform can be summed up as follows: ΔtOV = Δt1 + Δt2 + Δt3 The MAX6495/MAX6496/MAX6499 dissipate the most power during an overvoltage event when IOUT = 0. The maximum power dissipation can be approximated using the following equation: PDISS =VOV × 0.975 × I GATEPD × ∆t 1 ∆t OV The die-temperature increase is related to θJC (8.3°C/W and 8.5°C/W for the MAX6495/MAX6496/MAX6499, respectively) of the package when mounted correctly with a strong thermal contact to the circuit board. The MAX6495/MAX6496/MAX6499 thermal shutdown is governed by the equation: TJ = TA + PDISS (θJC +θCA) < +170°C Based on these calculations, the parameters of the MOSFET, the overvoltage threshold, the output load current, and the output capacitors are external variables affecting the junction temperature. If these parameters are fixed, the junction temperature can also be affected by increasing Δt3, which is the time the switch is on. By increasing the capacitance at the GATE pin, Δt3 increases as it increases the amount of time required to charge up this additional capacitance (75μA gate current). As a result, ΔtOV increases, thereby reducing the power dissipated (PDISS). Figure 5. MAX6495/MAX6496/MAX6499 Timing www.maximintegrated.com Maxim Integrated │  13 MAX6495–MAX6499 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET Typical Application Circuits DC-DC CONVERTER DC-DC CONVERTER IN IN OUT GND GATE 12V IN IN GATE 12V OUTFB IN MAX6495 OUTFB MAX6496 SHDN SHDN OVSET OVSET GATEP GND GND Figure 7. Overvoltage Limiter with Low-Voltage-Drop ReverseProtection Circuit (MAX6496) Figure 6. Overvoltage Limiter (MAX6495) DC-DC CONVERTER IN OUT EN GND DC-DC CONVERTER IN 12V GATE OUTFB 12V POKSET IN SHDN MAX6497 MAX6498 GND Figure 8. Overvoltage Protection to a DC-DC Converter (MAX6497/MAX6498) www.maximintegrated.com OUT GND GATE OUTFB IN R1 SHDN UVSET R2 OVSET POK OUT GND MAX6499 OVSET R3 CLEAR GND Figure 9. Overvoltage and Undervoltage Window Detector (MAX6499) Maxim Integrated │  14 MAX6495–MAX6499 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET Functional Diagrams IN IN THERMAL PROTECTION THERMAL PROTECTION UVLO UVLO 5V 10V CHARGE PUMP 5V 10V CHARGE PUMP IGATEP_SOURCE OVSET OVSET GATE GATE 1.24V OUTFB GATEP 1.24V OUTFB 10V SHDN SHDN MAX6495 MAX6496 GND GND Figure 10. Functional Diagram (MAX6495) Figure 11. Functional Diagram (MAX6496) IN IN THERMAL PROTECTION THERMAL PROTECTION UVLO UVLO 10V CHARGE PUMP 5V 10V CHARGE PUMP 5V OVSET GATE OVSET GATE 0.505V 1.24V OUTFB SHDN POKSET OUTFB UVSET SHDN 1.24V POK MAX6497 MAX6498 1.24V GND Figure 12. Functional Diagram (MAX6497/MAX6498) www.maximintegrated.com MAX6499 CLEAR GND Figure 13. Functional Diagram (MAX6499) Maxim Integrated │  15 MAX6495–MAX6499 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET Selector Guide p-CHANNEL DRIVER POK FUNCTION UNDERVOLTAGE LATCH/ AUTORETRY PACKAGE CODE OV Switch/Limiter — — — — T633-2 OV Switch/Limiter Yes — — — T833-2 MAX6497 OV Switch — Yes — Latch T833-2 MAX6498 OV Switch — Yes — Autoretry T833-2 MAX6499 OV/UV Switch/Limiter — — Yes Latch T833-2 PART Function MAX6495 MAX6496 Ordering Information PART PIN-PACKAGE Chip Information TOP MARK MAX6495ATT+T 6 TDFN-EP* AJM MAX6495ATT/V+T 6 TDFN-EP* AUG MAX6496ATA+T 8 TDFN-EP* AOF MAX6496ATA/V+T 8 TDFN-EP* AOF MAX6497ATA+T 8 TDFN-EP* AOC MAX6498ATA+T 8 TDFN-EP* AOD MAX6499ATA+T 8 TDFN-EP* AOE MAX6499ATA/V+T 8 TDFN-EP* AOE PROCESS: BiCMOS Note: All devices are specified over the -40°C to +125°C operating temperature range. +Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. *EP = Exposed pad. /V denotes an automotive qualified part. www.maximintegrated.com Maxim Integrated │  16 MAX6495–MAX6499 72V, Overvoltage-Protection Switches/Limiter Controllers with an External MOSFET Revision History REVISION NUMBER REVISION DATE PAGES CHANGED 0 7/05 Initial release 1 12/05 Corrected text and formula in the Detailed Description. 2 1/07 Updated text in the Applications Information. 3 12/08 Updated package codes in the Selector Guide. 1, 13 4 1/09 Added automotive qualified part for MAX6495. 1, 14 5 3/09 Updated Electrical Characteristics, added Peak Power Dissipation Limit section and new Figure 4. Renumbered subsequent figures throughout data sheet. 6 7/09 Corrected the MAX6495ATT/V+T top mark in the Ordering Information table from AJM to AUG. 7 8/09 Updated Undervoltage Monitoring (MAX6499) and Setting Overvoltage Thresholds sections. 8, 9 8 1/11 Added soldering temperature in the Absolute Maximum Ratings section and corrected equation. 2, 11 9 2/12 Added automotive package for MAX6499. 15 10 6/12 Added automotive package for MAX6496. 15 11 4/15 Updated Benefits and Features section. 1 12 12/15 Corrected error in data sheet that repeated MAX6496 and excluded MAX6495 1–15 13 6/17 Update pin descriptions and POKSET divider wording 7, 10 14 7/17 Added AEC-Q100 Qualified statement to Benefits and Features section 1 15 2/18 Added Package Information section 2 16 4/18 Updated the Benefits and Features section. 1 DESCRIPTION — 10, 11 9 3, 9, 10–15 2 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. ©  2018 Maxim Integrated Products, Inc. │  17