LT4356MP-1/LT4356MP-2 Surge Stopper FEATURES n n n n n n n n n n n n n DESCRIPTION Stops High Voltage Surges Adjustable Output Clamp Voltage Overcurrent Protection Wide Operation Range: 4V to 80V Reverse Input Protection to -60V Low 7A Shutdown Current, LT4356-1 Adjustable Fault Timer Controls N-Channel MOSFET Shutdown Pin Withstands -60V to 100V Fault Output Indication Guaranteed Operation -55C to 125C Auxiliary Amplifier for Level Detection Comparator or Linear Regulator Controller Available in 10-Pin MSOP or 16-Pin SO Packages APPLICATIONS n n n n Automotive/Avionic Surge Protection Hot Swap/Live Insertion High Side Switch for Battery Powered Systems Intrinsic Safety Applications L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and No RSENSE and ThinSOT are trademarks of Analog Devices, Inc. All other trademarks are the property of their respective owners. The LT(R)4356 surge stopper protects loads from high voltage transients. It regulates the output during an overvoltage event, such as load dump in automobiles, by controlling the gate of an external N-channel MOSFET. The output is limited to a safe value thereby allowing the loads to continue functioning. The LT4356MP also monitors the voltage drop between the VCC and SNS pins to protect against overcurrent faults. An internal amplifier limits the current sense voltage to 50mV. In either fault condition, a timer is started inversely proportional to MOSFET stress. If the timer expires, the FLT pin pulls low to warn of an impending power-down. If the condition persists, the MOSFET is turned off. After a cooldown period, the GATE pin pulls up turning on the MOSFET again. The auxiliary amplifier may be used as a voltage detection comparator or as a linear regulator controller driving an external PNP pass transistor. Back-to-back FETs can be used in lieu of a Schottky diode for reverse input protection, reducing voltage drop and power loss. A shutdown pin reduces the quiescent current to less than 7A for the LT4356-1 during shutdown. The LT4356-2 differs from the LT4356-1 during shutdown by reducing the quiescent current to 60A and keeping alive the auxiliary amplifier for uses such as an undervoltage lockout or always-on regulator. TYPICAL APPLICATION 4A, 12V Overvoltage Output Regulator 10m VIN 12V VOUT IRLR2908 80V INPUT SURGE 10 383k VCC SNS GATE 102k FB IN+ 4.99k 100k EN AOUT GND TMR VCC DC-DC CONVERTER LT4356S FLT CTMR = 6.8F ILOAD = 500mA VIN 20V/DIV OUT SHDN UNDERVOLTAGE Overvoltage Protector Regulates Output at 27V During Transient SHDN GND 12V VOUT 20V/DIV 27V ADJUSTABLE CLAMP 12V FAULT 100ms/DIV 4356mp12 TA01b 4356mp12 TA01 0.1F 4356mp12fc For more information www.linear.com/LT4356MP-1 1 LT4356MP-1/LT4356MP-2 ABSOLUTE MAXIMUM RATINGS (Notes 1 and 2) VCC, SHDN................................................. -60V to 100V SNS.............................. VCC - 30V or -60V to VCC + 0.3V OUT, AOUT, FLT, EN...................................... -0.3V to 80V GATE (Note 3)..................................-0.3V to VOUT + 10V FB, TMR, IN+................................................. -0.3V to 6V AOUT, EN, FLT, IN+.................................................. -3mA Operating Temperature Range LT4356M............................................. -55C to 125C Storage Temperature Range MS, SO............................................... -65C to 150C Lead Temperature (Soldering, 10 sec) MS, SO.............................................................. 300C PIN CONFIGURATION TOP VIEW TMR 1 16 IN+ FB 2 15 NC NC 3 14 AOUT TOP VIEW FB OUT GATE SNS VCC 1 2 3 4 5 10 9 8 7 6 TMR GND EN FLT SHDN OUT 4 GATE 5 MS PACKAGE 10-LEAD PLASTIC MSOP TJMAX = 125C, JA = 160C/W 13 NC 12 GND NC 6 11 EN SNS 7 10 FLT VCC 8 9 SHDN S PACKAGE 16-LEAD PLASTIC SO TJMAX = 150C, JA = 100C/W ORDER INFORMATION http://www.linear.com/product/LT4356MP-1#orderinfo LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT4356MPMS-1#PBF LT4356MPMS-1#TRPBF LTFGD 10-Lead Plastic MSOP -55C to 125C LT4356MPS-1#PBF LT4356MPS-1#TRPBF LT4356MPS-1 16-Lead Plastic SO -55C to 125C LT4356MPS-2#PBF LT4356MPS-2#TRPBF LT4356MPS-2 16-Lead Plastic SO -55C to 125C LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT4356MPMS-1 LT4356MPMS-1#TR LTFGD 10-Lead Plastic MSOP -55C to 125C LT4356MPS-1 LT4356MPS-1#TR LT4356MPS-1 16-Lead Plastic SO -55C to 125C LT4356MPS-2 LT4356MPS-2#TR LT4356MPS-2 16-Lead Plastic SO -55C to 125C Consult LTC Marketing for parts specified with wider operating temperature ranges. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix. 2 4356mp12fc For more information www.linear.com/LT4356MP-1 LT4356MP-1/LT4356MP-2 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 12V unless otherwise noted. SYMBOL PARAMETER VCC Operating Voltage Range ICC VCC Supply Current CONDITIONS MIN TYP MAX 80 V VSHDN = Float l 1 1.5 mA VSHDN = 0V, IN+ = 1.3V, LT4356MP-1 LT4356MP-1 l 7 7 25 40 A A VSHDN = 0V, IN+ = 1.3V, LT4356MP-2 LT4356MP-2 l 60 60 70 250 A A 0.3 0.8 1 2 mA mA 8 16 V V -38 -50 A A l 4 UNITS IR Reverse Input Current VSNS = VCC = -30V, SHDN Open VSNS = VCC = VSHDN = -30V l l VGATE GATE Pin Output High Voltage VCC = 4V; (VGATE - VOUT) 80V VCC 8V; (VGATE - VOUT) l l 4.5 10 IGATE(UP) GATE Pin Pull-Up Current VGATE = 12V; VCC = 12V VGATE = 48V; VCC = 48V l l -4 -4.5 -23 -30 IGATE(DN) GATE Pin Pull-Down Current Overvoltage, VFB = 1.4V, VGATE = 12V Overcurrent, VCC - VSNS = 120mV, VGATE = 12V Shutdown Mode, VSHDN = 0V, VGATE = 12V l l l 75 5 1.5 150 10 5 VFB FB Pin Servo Voltage VGATE = 12V; VOUT = 12V l 1.215 1.25 1.275 V IFB FB Pin Input Current VFB = 1.25V l 0.3 1 A VSNS Overcurrent Fault Threshold VSNS = (VCC - VSNS), VCC = 12V VSNS = (VCC - VSNS), VCC = 48V l l 42.5 43 50 51 55 56 mV mV ISNS SNS Pin Input Current VSNS = VCC = 12V to 48V l 5 10 ILEAK FLT, EN Pins Leakage Current AOUT Pin Leakage Current FLT, EN = 80V AOUT = 80V l ITMR TMR Pin Pull-Up Current VTMR = 1V, VFB = 1.5V, (VCC - VOUT) = 0.5V VTMR = 1V, VFB = 1.5V, (VCC - VOUT) = 75V VTMR = 1.3V, VFB = 1.5V VTMR = 1V, VSNS = 60mV, (VCC - VOUT) = 0.5V VTMR = 1V, VSNS = 60mV, (VCC - VOUT) = 80V l l l l l -1.5 -44 -3.5 -2.5 -195 TMR Pin Pull-Down Current VTMR = 1V, VFB = 1V, VSNS = 0V l VTMR TMR Pin Thresholds FLT From High to Low, VCC = 5V to 80V VGATE From Low to High, VCC = 5V to 80V l l VTMR Early Warning Period From FLT Going Low to GATE Going Low, VCC = 5V to 80V l 80 VIN+ IN+ Pin Threshold l 1.22 mA mA mA 22 A 2.5 4.5 A A -2.5 -50 -5.5 -4.5 -260 -4 -56 -8.5 -6.5 -315 A A A A A 1.5 2.2 2.7 A 1.22 0.48 1.25 0.5 1.28 0.52 V V 100 120 mV 1.25 1.28 V IIN IN+ Pin Input Current VIN l 0.3 1 A VOL FLT, EN Pins Output Low ISINK = 2mA ISINK = 0.1mA l l 2 300 8 800 V mV AOUT Pin Output Low ISINK = 2mA ISINK = 0.1mA l l 2 200 8 400 V mV + + = 1.25V 4356mp12fc For more information www.linear.com/LT4356MP-1 3 LT4356MP-1/LT4356MP-2 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 12V unless otherwise noted. SYMBOL PARAMETER CONDITIONS IOUT OUT Pin Input Current VOUT = VCC = 12V VOUT = VCC = 12V, VSHDN = 0V l l VOUT OUT Pin High Threshold VOUT = VCC - VOUT; EN from Low to High l VSHDN SHDN Pin Threshold VCC = 12V to 48V VSHDN(FLT) SHDN Pin Float Voltage MIN TYP MAX UNITS 200 6 300 14 A mA 0.25 0.5 0.7 V 0.6 0.4 1.4 l 1.7 2.1 V V VCC = 12V to 48V l 0.6 1.2 2.1 V ISHDN SHDN Pin Current VSHDN = 0V l -1 -4 -8 A tOFF(OC) Overcurrent Turn-Off Delay Time GATE from High to Low, VSNS = 0 120mV l 2 4 s tOFF(OV) Overvoltage Turn-Off Delay Time GATE from High to Low, VFB = 0 1.5V l 0.25 1 s Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to GND unless otherwise specified. Note 3: An internal clamp limits the GATE pin to a minimum of 10V above the OUT pin. Driving this pin to voltages beyond the clamp may damage the device. TYPICAL PERFORMANCE CHARACTERISTICS Specifications are at VCC = 12V, TA = 25C unless otherwise noted. ICC (Shutdown) vs VCC ICC vs VCC 60 600 ICC (A) ICC (A) 800 400 200 0 4 0 10 20 30 40 50 VCC (V) 60 70 80 4356mp12 G01 ICC (Shutdown) vs VCC 120 LT4356-1 50 100 40 80 ICC (A) 1000 30 60 20 40 10 20 0 0 10 20 30 40 50 VCC (V) 60 70 80 4356mp12 G02 LT4356-2 IN+ = 1.3V 0 0 10 20 30 40 50 VCC (V) 60 70 80 4356mp12 G03 4356mp12fc For more information www.linear.com/LT4356MP-1 LT4356MP-1/LT4356MP-2 TYPICAL PERFORMANCE CHARACTERISTICS Specifications are at VCC = 12V, TA = 25C unless otherwise noted. 300 30 20 ICC (A) 15 10 250 5 200 4 150 25 75 0 50 TEMPERATURE (C) 100 2 50 1 0 -50 125 4356mp12 G04 40 35 35 30 20 15 10 20 30 40 50 VCC (V) 60 70 12 15 10 VGATE (V) 4 2 -25 0 50 25 75 TEMPERATURE (C) 100 125 160 140 25 75 0 50 TEMPERATURE (C) 100 125 100 -50 4356mp12 G10 12 10 10 8 6 2 2 6 125 4356mp12 G09 10 IGATE (A) 8 12 14 16 4356mp12 G11 IGATE = -1A VCC = 8V 6 4 4 100 8 4 2 0 50 25 75 TEMPERATURE (C) VGATE vs Temperature 14 VOUT = 12V 0 -25 4356mp12 G08 12 0 4356mp12 G06 180 VGATE vs IGATE 6 0 -50 -25 14 8 125 120 4356mp12 G07 OVERCURRENT CONDITION VSNS = 120mV 100 OVERVOLTAGE CONDITION VFB = 1.5V 200 20 GATE Pull-Down Current vs Temperature 220 VGATE = VOUT = 12V 0 -50 80 0 50 25 75 TEMPERATURE (C) GATE Pull-Down Current vs Temperature 5 5 -25 4356mp12 G05 10 10 0 0 -50 125 25 25 IGATE (A) IGATE (A) 30 IGATE(DOWN) (mA) 100 GATE Pull-Up Current vs Temperature GATE Pull-Up Current vs VCC 0 0 50 25 75 TEMPERATURE (C) -25 VSHDN = 0V 3 100 5 -25 LT4356-2 IGATE(DOWN) (mA) ICC (A) 25 6 ISHDN (A) LT4356-1 0 -50 SHDN Current vs Temperature ICC (Shutdown) vs Temperature ICC (Shutdown) vs Temperature VGATE (V) 35 0 -50 VCC = 4V -25 0 50 25 75 TEMPERATURE (C) 100 125 4356mp12 G12 4356mp12fc For more information www.linear.com/LT4356MP-1 5 LT4356MP-1/LT4356MP-2 TYPICAL PERFORMANCE CHARACTERISTICS Overvoltage TMR Current vs (VCC - VOUT) VGATE vs VCC 48 14 12 TA = -45C 10 280 OVERVOLTAGE CONDITION VOUT = 5V 40 VTMR = 1V TA = 130C OVERCURRENT CONDITION VOUT = 0V 240 VTMR = 1V 200 32 ITMR (A) TA = 25C 8 6 ITMR (A) 16 VGATE (V) Overcurrent TMR Current vs (VCC - VOUT) 24 16 8 40 50 VCC (V) 60 70 0 80 10 20 30 40 50 VCC - VOUT (V) 60 70 0 80 3.0 OVERVOLTAGE, EARLY WARNING PERIOD 12 VFB = 1.5V VTMR = 1.3V 10 0 10 20 4356mp12 G14 TMR Pull-Down Current vs Temperature 14 30 40 50 VCC - VOUT (V) 60 70 80 4356mp12 G15 Output Low Voltage vs Current 4.0 VTMR = 1V 3.5 2.5 AOUT 3.0 2.0 ITMR (A) ITMR (A) 0 4356mp12 G13 Warning Period TMR Current vs VCC 8 6 2.5 1.5 FLT 2.0 EN 1.5 1.0 4 1.0 0.5 2 0 40 VOL (V) 30 120 80 4 2 I GATE = -1A VOUT = VCC 0 0 10 20 160 0 10 20 30 40 50 VCC (V) 60 70 0 -50 80 -25 4356mp12 G16 0 25 50 75 TEMPERATURE (C) 100 0 125 4.0 OVERVOLTAGE CONDITION VFB = 1.5V 0.5 2.0 1.0 1.5 CURRENT (mA) 2.5 3.0 4356mp12 G18 Reverse Current vs Reverse Voltage -20 OVERCURRENT CONDITION VSNS = 120mV 3.5 400 0 4356mp12 G17 Overcurrent Turn-Off Time vs Temperature Overvoltage Turn-Off Time vs Temperature 500 0.5 VCC = SNS -15 200 2.5 -10 2.0 -5 100 0 -50 ICC (mA) 300 tOFF (s) tOFF (ns) 3.0 1.5 -25 0 25 50 75 TEMPERATURE (C) 100 125 4356mp12 G19 1.0 -50 -25 0 25 50 75 TEMPERATURE (C) 100 125 4356mp12 G20 0 0 -20 -40 -60 -80 VCC (V) 4356mp12 G21 6 4356mp12fc For more information www.linear.com/LT4356MP-1 LT4356MP-1/LT4356MP-2 PIN FUNCTIONS AOUT (SO Package Only): Amplifier Output. Open collector output of the auxiliary amplifier. It is capable of sinking up to 2mA from 80V. The negative input of the amplifier is internally connected to a 1.25V reference. OUT: Output Voltage Sense Input. This pin senses the voltage at the source of the N-channel MOSFET and sets the fault timer current. When the OUT pin voltage reaches 0.7V away from VCC, the EN pin goes high impedance. EN: Open-Collector Enable Output. The EN pin goes high impedance when the voltage at the OUT pin is above (VCC - 0.7V), indicating the external MOSFET is fully on. The state of the pin is latched until the OUT pin voltage resets at below 0.5V and goes back up above 2V. The internal NPN is capable of sinking up to 3mA of current from 80V to drive an LED or opto-coupler. SHDN: Shutdown Control Input. The LT4356 can be shut down to a low current mode by pulling the SHDN pin below 0.4V. Pull this pin above 2.1V or disconnect it and allow the internal current source to turn the part back on. The leakage current to ground at the pin should be limited to no more than 1A if no pull-up device is used to turn the part on. The SHDN pin can be pulled up to 100V or below GND by 60V without damage. In shutdown, the auxiliary amplifier turns off in the LT4356-1 but continues operating in the LT4356-2. FB: Voltage Regulator Feedback Input. Connect this pin to the center tap of the output resistive divider connected between the OUT pin and ground. During an overvoltage condition, the GATE pin is servoed to maintain a 1.25V threshold at the FB pin. This pin is clamped internally to 7V. Tie to GND to disable the OV clamp. FLT: Open-Collector Fault Output. This pin pulls low after the voltage at the TMR pin has reached the fault threshold of 1.25V. It indicates the pass transistor is about to turn off because either the supply voltage has stayed at an elevated level for an extended period of time (voltage fault) or the device is in an overcurrent condition (current fault). The internal NPN is capable of sinking up to 3mA of current from 80V to drive an LED or opto-coupler. GATE: N-channel MOSFET Gate Drive Output. The GATE pin is pulled up by an internal charge pump current source and clamped to 14V above the OUT pin. Both voltage and current amplifiers control the GATE pin to regulate the output voltage and limit the current through the MOSFET. GND: Device Ground. IN+ (SO Package Only): Positive Input of the Auxiliary Amplifier. This amplifier can be used as a level detection comparator with external hysteresis or linear regulator controlling an external PNP transistor. This pin is clamped internally to 7V. Connect to ground if unused. SNS: Current Sense Input. Connect this pin to the output of the current sense resistor. The current limit circuit controls the GATE pin to limit the sense voltage between VCC and SNS pins to 50mV. At the same time the sense amplifier also starts a current source to charge up the TMR pin. This pin can be pulled below GND by up to 60V, though the voltage difference with the VCC pin must be limited to less than 30V. Connect to VCC if unused. TMR: Fault Timer Input. Connect a capacitor between this pin and ground to set the times for early warning, fault and cooldown periods. The current charging up this pin during fault conditions depends on the voltage difference between the VCC and OUT pins. When VTMR reaches 1.25V, the FLT pin pulls low to indicate the detection of a fault condition. If the condition persists, the pass transistor turns off when VTMR reaches the threshold of 1.35V. As soon as the fault condition disappears, the pull-up current stops and a 2A current starts to pull the TMR pin down. When VTMR reaches the retry threshold of 0.5V, the GATE pin pulls high turning back on the pass transistor. A minimum of 10nF capacitor is needed to compensate the loop. A 10V rated X7R capacitor is recommended for CTMR. VCC: Positive Supply Voltage Input. The positive supply input ranges from 4V to 80V for normal operation. It can also be pulled below ground potential by up to 60V during a reverse battery condition, without damaging the part. The supply current is reduced to 7A with all the functional blocks off. 4356mp12fc For more information www.linear.com/LT4356MP-1 7 LT4356MP-1/LT4356MP-2 BLOCK DIAGRAM VCC GATE + - 14V CHARGE PUMP + OUT FB - + 50mV SNS VA IA 1.25V - SHDN FLT AOUT OC 1.25V AUXILIARY AMPLIFIER SHDN RESTART OUT - + 1.35V + 0.5V EN CONTROL LOGIC GATEOFF IN+ OV FLT - VCC ITMR + - + 2A 1.25V TMR - GND 4356mp12 BD 8 4356mp12fc For more information www.linear.com/LT4356MP-1 LT4356MP-1/LT4356MP-2 OPERATION Some power systems must cope with high voltage surges of short duration such as those in automobiles. Load circuitry must be protected from these transients, yet high availability systems must continue operating during these events. The potential at the TMR pin starts decreasing as soon as the overvoltage condition disappears. When the voltage at the TMR pin reaches 0.5V the GATE pin begins rising, turning on the MOSFET. The FLT pin will then go to a high impedance state. The LT4356 is an overvoltage protection regulator that drives an external N-channel MOSFET as the pass transistor. It operates from a wide supply voltage range of 4V to 80V. It can also be pulled below ground potential by up to 60V without damage. The low power supply requirement of 4V allows it to operate even during cold cranking conditions in automotive applications. The internal charge pump turns on the N-channel MOSFET to supply current to the loads with very little power loss. Two MOSFETs can be connected back to back to replace an inline Schottky diode for reverse input protection. This improves the efficiency and increases the available supply voltage level to the load circuitry during cold crank. The fault timer allows the load to continue functioning during short transient events while protecting the MOSFET from being damaged by a long period of supply overvoltage, such as a load dump in automobiles. The timer period varies with the voltage across the MOSFET. A higher voltage corresponds to a shorter fault timer period, ensuring the MOSFET operates within its safe operating area (SOA). Normally, the pass transistor is fully on, powering the loads with very little voltage drop. When the supply voltage surges too high, the voltage amplifier (VA) controls the gate of the MOSFET and regulates the voltage at the source pin to a level that is set by the external resistive divider from the OUT pin to ground and the internal 1.25V reference. A current source starts charging up the capacitor connected at the TMR pin to ground. If the voltage at the TMR pin, VTMR, reaches 1.25V, the FLT pin pulls low to indicate impending turn-off due to the overvoltage condition. The pass transistor stays on until the TMR pin reaches 1.35V, at which point the GATE pin pulls low turning off the MOSFET. The LT4356 senses an overcurrent condition by monitoring the voltage across an optional sense resistor placed between the VCC and SNS pins. An active current limit circuit (IA) controls the GATE pin to limit the sense voltage to 50mV. A current is also generated to start charging up the TMR pin. This current is about 5 times the current generated during an overvoltage event. The FLT pin pulls low when the voltage at the TMR pin reaches 1.25V and the MOSFET is turned off when it reaches 1.35V. An auxiliary amplifier is provided with the negative input connected to an internal 1.25V reference. The output pulldown device is capable of sinking up to 2mA of current allowing it to drive an LED or opto coupler. This amplifier can be configured as a linear regulator controller driving an external PNP transistor or a comparator function to monitor voltages. A shutdown pin turns off the pass transistor and reduces the supply current to less than 7A for the LT4356-1. The supply current drops down to 60A while keeping the internal reference and the auxiliary amplifier active for the LT4356-2 version during shutdown. 4356mp12fc For more information www.linear.com/LT4356MP-1 9 LT4356MP-1/LT4356MP-2 APPLICATIONS INFORMATION The LT4356 can limit the voltage and current to the load circuitry during supply transients or overcurrent events. The total fault timer period should be set to ride through short overvoltage transients while not causing damage to the pass transistor. The selection of this N-channel MOSFET pass transistor is critical for this application. It must stay on and provide a low impedance path from the input supply to the load during normal operation and then dissipate power during overvoltage or overcurrent conditions. The following sections describe the overcurrent and the overvoltage faults, and the selection of the timer capacitor value based on the required warning time. The selection of the N-channel MOSFET pass transistor is discussed next. Auxiliary amplifier, reverse input, and the shutdown functions are covered after the MOSFET selection. External component selection is discussed in detail in the Design Example section. Overvoltage Fault The LT4356 limits the voltage at the OUT pin during an overvoltage situation. An internal voltage amplifier regulates the GATE pin voltage to maintain a 1.25V threshold at the FB pin. During this period of time, the power MOSFET is still on and continues to supply current to the load. This allows uninterrupted operation during short overvoltage transient events. When the voltage regulation loop is engaged for longer than the time-out period, set by the timer capacitor connected from the TMR pin to ground, an overvoltage fault is detected. The GATE pin is pulled down to the OUT pin by a 150mA current. After the fault condition has disappeared and a cooldown period has transpired, the GATE pin starts to pull high again. This prevents the power MOSFET from being damaged during a long period of overvoltage, such as during load dump in automobiles. 10 Overcurrent Fault The LT4356 features an adjustable current limit that protects against short circuits or excessive load current. During an overcurrent event, the GATE pin is regulated to limit the current sense voltage across the VCC and SNS pins to 50mV. An overcurrent fault occurs when the current limit circuitry has been engaged for longer than the time-out delay set by the timer capacitor. The GATE pin is then immediately pulled low by a 10mA current to GND turning off the MOSFET. After the fault condition has disappeared and a cooldown period has transpired, the GATE pin is allowed to pull back up and turn on the pass transistor. Fault Timer The LT4356 includes an adjustable fault timer pin. Connecting a capacitor from the TMR pin to ground sets the delay timer period before the MOSFET is turned off. The same capacitor also sets the cooldown period before the MOSFET is allowed to turn back on after the fault condition has disappeared. Once a fault condition, either overvoltage or overcurrent, is detected, a current source charges up the TMR pin. The current level varies depending on the voltage drop across the drain and source terminals of the power MOSFET(VDS), which is typically from the VCC pin to the OUT pin. This scheme takes better advantage of the available Safe Operating Area (SOA) of the MOSFET than would a fixed timer current. The timer function operates down to VCC = 5V across the whole temperature range. 4356mp12fc For more information www.linear.com/LT4356MP-1 LT4356MP-1/LT4356MP-2 APPLICATIONS INFORMATION Fault Timer Current The timer current starts at around 2A with 0.5V or less of VDS, increasing linearly to 50A with 75V of VDS during an overvoltage fault (Figure 1). During an overcurrent fault, it starts at 4A with 0.5V or less of VDS but increases to 260A with 80V across the MOSFET (Figure 2). This arrangement allows the pass transistor to turn off faster during an overcurrent event, since more power is dissipated during this condition. Refer to the Typical Performance Characteristics section for the timer current at different VDS in both overvoltage and overcurrent events. VTMR(V) When the voltage at the TMR pin, VTMR, reaches the 1.25V threshold, the FLT pin pulls low to indicate the detection of a fault condition and provide warning to the load of the impending power loss. In the case of an overvoltage fault, the timer current then switches to a fixed 5A. The interval between FLT asserting low and the MOSFET turning off is given by: t WARNING = CTMR * 100mV 5A ITMR = 5A ITMR = 5A 1.35 1.25 VDS = 75V (ITMR = 50A) VDS = 10V (ITMR = 8A) 0.50 TIME tFLT = 15ms/F tWARNING = 20ms/F tFLT = 93.75ms/F tWARNING = 20ms/F TOTAL FAULT TIMER = tFLT + tWARNING 4356mp12 F01 Figure 1. Overvoltage Fault Timer Current VTMR(V) 1.35 1.25 VDS = 80V (ITMR = 260A) 0.50 tFLT = 2.88ms/F VDS = 10V (ITMR = 35A) TIME tWARNING = 0.38ms/F tFLT = 21.43ms/F TOTAL FAULT TIMER = tFLT + tWARNING tWARNING = 2.86ms/F 4356mp12 F02 Figure 2. Overcurrent Fault Timer Current 4356mp12fc For more information www.linear.com/LT4356MP-1 11 LT4356MP-1/LT4356MP-2 APPLICATIONS INFORMATION This fixed early warning period allows the systems to perform necessary backup or house-keeping functions before the power supply is cut off. After VTMR crosses the 1.35V threshold, the pass transistor turns off immediately. Note that during an overcurrent event, the timer current is not reduced to 5A after VTMR has reached 1.25V threshold, since it would lengthen the overall fault timer period and cause more stress on the power MOSFET. As soon as the fault condition has disappeared, a 2A current starts to discharge the timer capacitor to ground. When VTMR reaches the 0.5V threshold, the internal charge pump starts to pull the GATE pin high, turning on the MOSFET. The TMR pin is then actively regulated to 0.5V until the next fault condition appears. The total cooldown timer period is given by: tCOOL C * 0.85V = TMR 2A MOSFET Selection The LT4356 drives an N-channel MOSFET to conduct the load current. The important features of the MOSFET are on-resistance RDS(ON), the maximum drain-source voltage V(BR)DSS, the threshold voltage, and the SOA. The maximum allowable drain-source voltage must be higher than the supply voltage. If the output is shorted to ground or during an overvoltage event, the full supply voltage will appear across the MOSFET. The gate drive for the MOSFET is guaranteed to be more than 10V and less than 16V for those applications with VCC higher than 8V. This allows the use of standard threshold voltage N-channel MOSFETs. For systems with VCC less than 8V, a logic level MOSFET is required since the gate drive can be as low as 4.5V. The SOA of the MOSFET must encompass all fault conditions. In normal operation the pass transistor is fully on, dissipating very little power. But during either overvoltage or overcurrent faults, the GATE pin is servoed to regulate either the output voltage or the current through the MOSFET. Large current and high voltage drop across the MOSFET can coexist in these cases. The SOA curves of the MOSFET must be considered carefully along with the selection of the fault timer capacitor. Transient Stress in the MOSFET During an overvoltage event, the LT4356 drives a series pass MOSFET to regulate the output voltage at an acceptable level. The load circuitry may continue operating throughout this interval, but only at the expense of dissipation in the MOSFET pass device. MOSFET dissipation or stress is a function of the input voltage waveform, regulation voltage and load current. The MOSFET must be sized to survive this stress. Most transient event specifications use the model shown in Figure 3. The idealized waveform comprises a linear ramp of rise time tr, reaching a peak voltage of VPK and exponentially decaying back to VIN with a time constant of t. A common automotive transient specification has constants of tr = 10s, VPK = 80V and t = 1ms. A surge condition known as "load dump" has constants of tr = 5ms, VPK = 60V and t = 200ms. VPK VIN tr 4356mp12 F03 Figure 3. Prototypical Transient Waveform 12 4356mp12fc For more information www.linear.com/LT4356MP-1 LT4356MP-1/LT4356MP-2 APPLICATIONS INFORMATION MOSFET stress is the result of power dissipated within the device. For long duration surges of 100ms or more, stress is increasingly dominated by heat transfer; this is a matter of device packaging and mounting, and heatsink thermal mass. This is analyzed by simulation, using the MOSFET thermal model. For short duration transients of less than 100ms, MOSFET survival is increasingly a matter of safe operating area (SOA), an intrinsic property of the MOSFET. SOA quantifies the time required at any given condition of VDS and ID to raise the junction temperature of the MOSFET to its rated maximum. MOSFET SOA is expressed in units of watt-squared-seconds (P2t). This figure is essentially constant for intervals of less than 100ms for any given device type, and rises to infinity under DC operating conditions. Destruction mechanisms other than bulk die temperature distort the lines of an accurately drawn SOA graph so that P2t is not the same for all combinations of ID and VDS. In particular P2t tends to degrade as VDS approaches the maximum rating, rendering some devices useless for absorbing energy above a certain voltage. Calculating Transient Stress To select a MOSFET suitable for any given application, the SOA stress must be calculated for each input transient which shall not interrupt operation. It is then a simple matter to chose a device which has adequate SOA to survive the maximum calculated stress. P2t for a prototypical transient waveform is calculated as follows (Figure 4). VPK VREG VIN tr 4356mp12 F04 Figure 4. Safe Operating Area Required to Survive Prototypical Transient Waveform Typically VREG VIN and t >> tr simplifying the above to P2 t = 1 2 ILOAD 2 ( VPK - VREG ) t 2 (W 2s) For the transient conditions of VPK = 80V, VIN = 12V, VREG = 16V, tr = 10s and t = 1ms, and a load current of 3A, P2t is 18.4W2s--easily handled by a MOSFET in a D-pak package. The P2t of other transient waveshapes is evaluated by integrating the square of MOSFET power versus time. Calculating Short-Circuit Stress SOA stress must also be calculated for short-circuit conditions. Short-circuit P2t is given by: P2t = (VIN * VSNS/RSNS)2 * tTMR (W2s) where, VSNS is the SENSE pin threshold, and tTMR is the overcurrent timer interval. For VIN = 14.7V, VSNS = 50mV, RSNS = 12m and CTMR = 100nF, P2t is 6.6W2s--less than the transient SOA Let calculated in the previous example. Nevertheless, to account for circuit tolerances this figure should be doua = VREG - VIN bled to 13.2W2s. b = VPK - VIN (VIN = Nominal Input Voltage) Limiting Inrush Current and GATE Pin Compensation Then The LT4356 limits the inrush current to any load capaci3 tance by controlling the GATE pin voltage slew rate. An 1 (b - a) 1 2 b P 2 t = ILOAD 2 tr + t 2a ln + 3a 2 +b2 - 4ab external capacitor can be connected from GATE to ground 3 b 2 a to slow down the inrush current further at the expense of slower turn-off time. The gate capacitor is set at: C1 = IGATE(UP) IINRUSH * CL 4356mp12fc For more information www.linear.com/LT4356MP-1 13 LT4356MP-1/LT4356MP-2 APPLICATIONS INFORMATION The LT4356 does not need extra compensation components at the GATE pin for stability during an overvoltage or overcurrent event. With transient input voltage step faster than 5V/s, a gate capacitor, C1, to ground is needed to prevent self enhancement of the N-channel MOSFET. The extra gate capacitance slows down the turn-off time during fault conditions and may allow excessive current during an output short event. An extra resistor, R1, in series with the gate capacitor can improve the turn-off time. A diode, D1, should be placed across R1 with the cathode connected to C1 as shown in Figure 5. The amplifier can also be configured as a low dropout linear regulator controller. With an external PNP transistor, such as 2N2905A, it can supply up to 100mA of current with only a few hundred mV of dropout voltage. Current limit can be easily included by adding two diodes and one resistor (Figure 6). RLIM *4.7 INPUT 2N2905A OR BCP53 2.5V OUTPUT 150mA MAX 10F R6 100k * OPTIONAL FOR CURRENT LIMIT D1* BAV99 11 AOUT Q1 LT4356S D1 IN4148W 12 IN+ 4356 F06 R3 R4 249k VOUT = 1.25 47nF ILIM R4 + R5 R5 0.7 RLIM R5 249k R1 C1 GATE Reverse Input Protection LT4356S 4356mp F05 Figure 5 Auxiliary Amplifier An uncommitted amplifier is included in the LT4356 to provide flexibility in the system design. With the negative input connected internally to the 1.25V reference, the amplifier can be connected as a level detect comparator with external hysteresis. The open collector output pin, AOUT, is capable of driving an opto or LED. It can also interface with the system via a pull-up resistor to a supply voltage up to 80V. Another use is to implement undervoltage lockout, as shown in the typical application "Overvoltage Regulator with Undervoltage Lockout." In shutdown, the auxiliary amplifier turns off in the LT4356-1 but continues operating in the LT4356-2. 14 Figure 6. Auxiliary LDO Output with Optional Current Limit A blocking diode is commonly employed when reverse input potential is possible, such as in automotive applications. This diode causes extra power loss, generates heat, and reduces the available supply voltage range. During cold crank, the extra voltage drop across the diode is particularly undesirable. The LT4356 is designed to withstand reverse voltage without damage to itself or the load. The VCC, SNS, and SHDN pins can withstand up to 60V of DC voltage below the GND potential. Back-to-back MOSFETs must be used to eliminate the current path through their body diodes (Figure 7). Figure 8 shows the approach with a P-channel MOSFET in place of Q2. 4356mp12fc For more information www.linear.com/LT4356MP-1 LT4356MP-1/LT4356MP-2 APPLICATIONS INFORMATION RSNS 10m VIN 12V Q2 IRLR2908 D2* SMAJ58CA R4 R5 10 1M Q3 2N3904 D1 1N4148 8 Q1 IRLR2908 VOUT 12V, 3A CLAMPED AT 16V R3 10 R1 59k R7 10k 7 SNS 4 OUT 5 GATE VCC FB 2 R2 4.99k LT4356S 9 14 16 SHDN FLT AOUT IN+ GND EN TMR 12 1 *DIODES INC. 10 RSNS 10m Q2 Si4435 4356mp12 F07 CTMR 0.1F Q1 IRLR2908 VOUT 12V, 3A CLAMPED AT 16V D1 1N5245 15V D2* SMAJ58CA R3 10 R6 10k 7 SNS 8 5 GATE The SHDN pin can be pulled up to VCC or below GND by up to 60V without damaging the pin. Leaving the pin open allows an internal current source to pull it up and turn on the part while clamping the pin to 2.5V. The leakage current at the pin should be limited to no more than 1A if no pull-up device is used to help turn it on. The LT4356 is guaranteed to be safe from damage with supply voltages up to 100V. Nevertheless, voltage transients above 100V may cause permanent damage. During a short-circuit condition, the large change in current flowing through power supply traces and associated wiring can cause inductive voltage transients which could exceed 100V. To minimize the voltage transients, the power trace parasitic inductance should be minimized by using wide traces. A small surge suppressor, D2, in Figure 9, at the input will clamp the voltage spikes. R1 59k 4 OUT FB VCC The LT4356 can be shut down to a low current mode when the voltage at the SHDN pin goes below the shutdown threshold of 0.6V. The quiescent current drops to 7A for the LT4356-1 and 60A for the LT4356-2 which leaves the auxiliary amplifier on. Supply Transient Protection 11 Figure 7. Overvoltage Regulator with N-channel MOSFET Reverse Input Protection VIN 12V Shutdown RSNS 10m VIN CL* 22F D2 SMAJ58A 2 R2 4.99k 9 14 16 LT4356S 8 SHDN AOUT IN+ FLT GND 12 *DIODES INC. EN TMR 1 Q1 IRLR2908 10 11 4356mp12 F08 CTMR 0.1F R4 383k 9 16 VCC FB UNDERVOLTAGE 2 SHDN IN+ R2 4.99k LT4356S R5 100k EN 14 R1 59k R3 10 7 5 4 SNS GATE OUT AOUT GND 12 Figure 8. Overvoltage Regulator with P-channel MOSFET Reverse Input Protection TMR 1 FLT 4356mp12 F09 CTMR 47nF 11 10 VCC DC-DC CONVERTER SHDN GND FAULT *SANYO 25CE22GA Figure 9. Overvoltage Regulator with Low-Battery Detection 4356mp12fc For more information www.linear.com/LT4356MP-1 15 LT4356MP-1/LT4356MP-2 APPLICATIONS INFORMATION A total bulk capacitance of at least 22F low ESR electrolytic is required close to the source pin of MOSFET Q1. In addition, the bulk capacitance should be at least 10 times larger than the total ceramic bypassing capacitor on the input of the DC/DC converter. Layout Considerations To achieve accurate current sensing, Kelvin connection to the current sense resistor (RSNS in Figure 9) is recommended. The minimum trace width for 1oz copper foil is 0.02" per amp to ensure the trace stays at a reasonable temperature. 0.03" per amp or wider is recommended. Note that 1oz copper exhibits a sheet resistance of about 530/square. Small resistances can cause large errors in high current applications. Noise immunity will be improved significantly by locating resistive dividers close to the pins with short VCC and GND traces. RSNS = As a design example, take an application with the following specifications: VCC = 8V to 14V DC with transient up to 80V, VOUT 16V, current limit (ILIM) at 5A, low battery detection at 6V, and 1ms of overvoltage early warning (Figure 9). First, calculate the resistive divider value to limit VOUT to 16V during an overvoltage event: 1.25V * (R1 + R2) =16V R2 50mV 50mV = = 10m ILIM 5A CTMR is then chosen for 1ms of early warning time: CTMR = 1ms * 5A = 50nF 100mV The closest standard value for CTMR is 47nF. Finally, calculate R4 and R5 for the 6V low battery threshold detection: 6V = 1.25V * (R4 + R5) R5 Choose 100k for R5. R4 = Design Example VREG = Next calculate the sense resistor, RSNS, value: (6V - 1.25V ) * R5 1.25V = 380k Select 383k for R4. The pass transistor, Q1, should be chosen to withstand the output short condition with VCC = 14V. The total overcurrent fault time is: tOC = 47nF * 0.85V = 0.878ms 45.5A The power dissipation on Q1 equals to: Set the current through R1 and R2 during the overvoltage condition to 250A. 1.25V R2 = = 5k 250A P= 14V * 50mV = 70W 10m These conditions are well within the Safe Operating Area of IRLR2908. Choose 4.99k for R2. R1 = (16V - 1.25V ) * R2 1.25V = 58.88k The closest standard value for R1 is 59k. 16 4356mp12fc For more information www.linear.com/LT4356MP-1 LT4356MP-1/LT4356MP-2 TYPICAL APPLICATIONS Wide Input Range 5V to 28V Hot Swap with Undervoltage Lockout RSNS 20m VIN Q1 SUD50N03-10 VOUT 100F R3 10 R6 118k C1 47nF 8 VCC 9 14 16 7 SNS 5 GATE 4 OUT FB SHDN 2 AOUT IN+ LT4356S-1 R7 49.9k FLT GND 12 TMR 1 EN 10 11 4356mp12 TA02 CTMR 1F 24V Overvoltage Regulator Withstands 150V at VIN VIN 24V Q1 IRF640 R9 1k 1W R3 10 5 GATE 7 SNS 8 D2* SMAT70A R1 118k 4 OUT FB VCC 2 R2 4.99k 9 10 11 LT4356S SHDN FLT EN GND 12 *DIODES INC. VOUT CLAMPED AT 32V TMR 1 4356mp12 TA03 CTMR 0.1F 4356mp12fc For more information www.linear.com/LT4356MP-1 17 LT4356MP-1/LT4356MP-2 TYPICAL APPLICATIONS Overvoltage Regulator with Undervoltage Lockout RSNS 20m VIN D2* SMAJ58A R6 280k R4 1M 9 R5 1M 14 16 Q1 IRLR2908 8 7 VCC SNS VOUT CLAMPED AT 16V R3 10 5 GATE R1 59k 4 OUT FB SHDN 2 R2 4.99k AOUT IN + LT4356S-2 R7 100k FLT GND *DIODES INC. EN TMR 12 1 10 11 4356mp12 TA04 CTMR 0.1F Overvoltage Regulator with Low Battery Detection and Output Keep Alive During Shutdown 1k 0.5W RSNS 10m VIN 12V D2* SMAJ58A Q1 IRLR2908 R3 10 R4 402k 8 16 R5 105k 9 *DIODES INC. 7 SNS 5 GATE VOUT 12V, 4A CLAMPED AT 16V Q2 VN2222 4 OUT VCC IN+ FB LT4356S AOUT FLT SHDN GND 12 EN TMR 1 R1 294k D1 1N4746A 18V 1W 2 14 R2 VDD 24.9k R6 47k LBO 10 11 4356mp12 TA05 CTMR 0.1F 18 4356mp12fc For more information www.linear.com/LT4356MP-1 LT4356MP-1/LT4356MP-2 TYPICAL APPLICATIONS 2.5A, 48V Hot Swap with Overvoltage Output Regulation at 72V and UV Shutdown at 35V RSNS 15m VIN 48V Q1 FDB3632 D2* SMAT70A R4 140k R3 10 VOUT 48V 2.5A R6 100k CL 300F C1 6.8nF 8 VCC D1 1N4714 BV = 33V 9 7 5 SNS GATE 4 OUT IN SHDN + 16 R5 4.02k R8 47k LT4356S 10 11 R7 1M FB R1 226k 2 R2 4.02k FLT EN GND *DIODES INC. AOUT TMR 12 1 14 PWRGD 4356mp12 TA06 CTMR 0.1F 2.5A, 28V Hot Swap with Overvoltage Output Regulation at 36V and UV Shutdown at 15V RSNS 15m VIN 28V Q1 FDB3632 D2* SMAT70A R4 113k R3 10 VOUT 28V 2.5A R6 27k CL 300F C1 6.8nF D1 1N4700 BV = 13V 9 8 VCC 7 5 SNS GATE 4 OUT 16 IN+ SHDN R5 4.02k R8 47k LT4356S 10 11 *DIODES INC. R7 1M FB 2 R2 4.02k FLT EN R1 110k GND 12 TMR 1 AOUT 14 PWRGD 4356mp12 TA07 CTMR 0.1F 4356mp12fc For more information www.linear.com/LT4356MP-1 19 LT4356MP-1/LT4356MP-2 TYPICAL APPLICATIONS Overvoltage Regulator with Reverse Input Protection Up to -80V RSNS 10m Q2 IRLR2908 VIN 12V Q3 2N3904 D2* R4 SMAJ58CA 10 R5 1M 8 D1 1N4148 Q1 IRLR2908 R7 10k R3 10 5 GATE 7 SNS VCC VOUT 12V, 3A CLAMPED AT 16V 4 OUT FB 2 R1 59k R2 4.99k D3** IN4148 LT4356S 9 14 16 SHDN IN+ * DIODES INC. ** OPTIONAL COMPONENT FOR REDUCED STANDBY CURRENT 20 FLT AOUT GND 12 EN TMR 1 10 11 4356mp12 TA08 CTMR 0.1F 4356mp12fc For more information www.linear.com/LT4356MP-1 LT4356MP-1/LT4356MP-2 PACKAGE DESCRIPTION Please refer to http://www.linear.com/product/LT4356MP-1#packaging for the most recent package drawings. MS Package 10-Lead Plastic MSOP (Reference LTC DWG # 05-08-1661) 0.889 0.127 (.035 .005) 5.23 (.206) MIN 3.20 - 3.45 (.126 - .136) 3.00 0.102 (.118 .004) (NOTE 3) 0.50 0.305 0.038 (.0197) (.0120 .0015) BSC TYP RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 10 9 8 7 6 3.00 0.102 (.118 .004) (NOTE 4) 4.90 0.152 (.193 .006) DETAIL "A" 0.497 0.076 (.0196 .003) REF 0 - 6 TYP GAUGE PLANE 1 2 3 4 5 0.53 0.152 (.021 .006) DETAIL "A" 0.18 (.007) SEATING PLANE 0.86 (.034) REF 1.10 (.043) MAX 0.17 - 0.27 (.007 - .011) TYP 0.50 (.0197) BSC NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 0.1016 0.0508 (.004 .002) MSOP (MS) 0307 REV E 4356mp12fc For more information www.linear.com/LT4356MP-1 21 LT4356MP-1/LT4356MP-2 PACKAGE DESCRIPTION Please refer to http://www.linear.com/product/LT4356MP-1#packaging for the most recent package drawings. S Package 16-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .386 - .394 (9.804 - 10.008) NOTE 3 .045 .005 .050 BSC 16 N .245 MIN 14 13 12 11 10 9 N .160 .005 .150 - .157 (3.810 - 3.988) NOTE 3 .228 - .244 (5.791 - 6.197) 1 .030 .005 TYP 15 2 3 N/2 N/2 RECOMMENDED SOLDER PAD LAYOUT 1 .010 - .020 x 45 (0.254 - 0.508) .008 - .010 (0.203 - 0.254) 2 3 4 5 .053 - .069 (1.346 - 1.752) NOTE: 1. DIMENSIONS IN .014 - .019 (0.355 - 0.483) TYP 7 8 .004 - .010 (0.101 - 0.254) 0 - 8 TYP .016 - .050 (0.406 - 1.270) 6 .050 (1.270) BSC S16 0502 INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) 22 4356mp12fc For more information www.linear.com/LT4356MP-1 LT4356MP-1/LT4356MP-2 REVISION HISTORY (Revision history begins at Rev A) REV DATE DESCRIPTION PAGE NUMBER A 05/10 Revised Features and Description 1 Added parameters to VOL in the Electrical Characteristics section 3 Rearranged Typical Performance Characteristics 4 Revised Pin Functions section 7 Made minor text edits to the Operation section Replaced Figure 6 and text edits in the Applications Information section B 01/12 Revised Max value for IGATE(UP) current at VCC = 12V Correct part number C 09/17 Updated TMR pin function with minimum recommended capacitance 9 13-20 3 10, 14 7 4356mp12fc Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. For more information www.linear.com/LT4356MP-1 23 LT4356MP-1/LT4356MP-2 TYPICAL APPLICATION Overvoltage Regulator with Linear Regulator Up to 100mA Q2 2N2905A RSNS 10m VIN 12V Q1 IRLR2908 D2* SMAJ58A R6 100k 14 9 R1 59k 4 OUT VCC FB 2 R2 4.99k LT4356S AOUT 16 IN+ SHDN FLT GND *DIODES INC. 2.5V, 100mA VOUT 12V, 3A CLAMPED AT 16V R3 10 5 GATE 7 SNS 8 C5 10F 12 TMR 1 EN 10 R4 249k C3 47nF R5 249k 11 4356mp12 TA09 CTMR 0.1F RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1641-1/LT1641-2 Positive High Voltage Hot Swap Controllers Active Current Limiting, Supplies From 9V to 80V LTC 1696 Overvoltage Protection Controller ThinSOTTM Package, 2.7V to 28V LTC1735 High Efficiency Synchronous Step-Down Switching Regulator Output Fault Protection, 16-Pin SSOP LTC1778 No RSENSETM Wide Input Range Synchronous Step-Down Controller Up to 97% Efficiency, 4V VIN 36V, 0.8V VOUT (0.9)(VIN), IOUT Up to 20A LTC2909 Triple/Dual Inputs UV/OV Negative Monitor Pin Selectable Input Polarity Allows Negative and OV Monitoring LTC2912/LTC2913 Single/Dual UV/OV Voltage Monitor Ads UV and OV Trip Values, 1.5% Threshold Accuracy LTC2914 Quad UV/OV Monitor For Positive and Negative Supplies (R) LTC3727/LTC3727-1 2-Phase, Dual, Synchronous Controller 4V VIN 36V, 0.8V VOUT 14V LTC3827/LTC3827-1 Low IQ, Dual, Synchronous Controller 4V VIN 36V, 0.8V VOUT 10V, 80A Quiescent Current LTC3835/LTC3835-1 Low IQ, Synchronous Step-Down Controller LT3845 Low IQ, Synchronous Step-Down Controller Single Channel LTC3827/LTC3827-1 LTC3850 Dual, 550kHz, 2-Phase Sychronous Step-Down Controller Dual 180 Phased Controllers, VIN 4V to 24V, 97% Duty Cycle, 4mm x 4mm QFN-28, SSOP-28 Packages LT4256 Positive 48V Hot Swap Controller with Open-Circuit Detect Foldback Current Limiting, Open-Circuit and Overcurrent Fault Output, Up to 80V Supply LTC4260 Positive High Voltage Hot Swap Controller with ADC and I2C Wide Operating Range 8.5V to 80V LTC4352 Ideal MOSFET ORing Diode External N-channel MOSFETs Replace ORing Diodes, 0V to 18V Operation LTC4354 Negative Voltage Diode-OR Controller Controls Two N-channel MOSFETs, 1s Turn-Off, 80V Operation LTC4355 Positive Voltage Diode-OR Controller Controls Two N-channel MOSFETs, 0.5s Turn-Off, 80V Operation 24 4V VIN 60V, 1.23V VOUT 36V, 120A Quiescent Current 4356mp12fc LT 0917 REV C * PRINTED IN USA For more information www.linear.com/LT4356MP-1 www.linear.com/LT4356MP-1 (c) LINEAR TECHNOLOGY CORPORATION 2009