LT4356CDE-2

LT4356-1 LINEAR | Alldatasheet

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Technical content

APPLICATIONS

The L T®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 con- tinue functioning. The L T4356 also monitors the voltage drop between the V CC and SNS pins to protect against overcurrent faults. An internal amplifi er 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 FL T pin pulls low to warn of an impend- ing power down. If the condition persists, the MOSFET is turned off. After a cool down period, the GATE pin pulls up turning on the MOSFET again. The auxiliary amplifi er 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 7μA for the L T4356-1 during shutdown. The L T4356-2 differs from the L T4356-1 during shutdown by reducing the quiescent current to 60μA and keeping alive the auxiliary amplifi er for uses such as an undervoltage lockout or always-on regulator . n Automotive/Avionic Surge Protection n Hot Swap/Live Insertion n High Side Switch for Battery Powered Systems n Intrinsic Safety Applications n Stops High Voltage Surges n Adjustable Output Clamp Voltage n Overcurrent Protection n Wide Operation Range: 4V to 80V n Reverse Input Protection to –60V n Low 7μA Shutdown Current, L T4356-1 n Adjustable Fault Timer n Controls N-channel MOSFET n Shutdown Pin Withstands –60V to 100V n Fault Output Indication n Guaranteed Operation to 125°C n Auxiliary Amplifi er for Level Detection Comparator or Linear Regulator Controller n Available in (4mm × 3mm) 12-Pin DFN, 10-Pin MSOP or 16-Pin SO Packages 4A, 12V Overvoltage Output Regulator Overvoltage Protector Regulates Output at 27V During T ransient 0.1μF 10Ω 10mΩ IRLR2908VIN 12V

4356 TA01

4.99k 383k 100k 102k 100ms/DIV

4356 TA01b

80V INPUT SURGE CTMR = 6.8μF ILOAD = 500mA 27V ADJUSTABLE CLAMP 12V 12V TYPICAL APPLICATION L, L T , L TC, L TM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.

Operating Temperature Range IN AOUT GND EN FLT SHDN TMR FB OUT GATE SNS V CC TOP VIEW DE PACKAGE 12-LEAD (4mm s 3mm) PLASTIC DFN TJMAX = 125°C, θJA = 43°C/W EXPOSED PAD (PIN 13) PCB GND CONNECTION OPTIONAL FB OUT GATE SNS V CC TMR GND EN FLT SHD N TOP VIEW MS PACKAGE 10-LEAD PLASTIC MSOP TJMAX = 125°C, θJA = 120°C/W TOP VIEW S PACKAGE 16-LEAD PLASTIC SO TMR FB NC OUT GATE NC SNS V CC IN+ NC A OUT NC GND EN FLT SHD N TJMAX = 150°C, θJA = 100°C/W Storage Temperature Range Lead Temperature (Soldering, 10 sec) ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Notes 1 and 2)

LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE L T4356CDE-1#PBF L T4356CDE-1#TRPBF 43561 12-Lead (4mm × 3mm) Plastic DFN 0°C to 70°C L T4356IDE-1#PBF L T4356IDE-1#TRPBF 43561 12-Lead (4mm × 3mm) Plastic DFN –40°C to 85°C L T4356HDE-1#PBF L T4356HDE-1#TRPBF 43561 12-Lead (4mm × 3mm) Plastic DFN –40°C to 125°C L T4356CDE-2#PBF L T4356CDE-2#TRPBF 43562 12-Lead (4mm × 3mm) Plastic DFN 0°C to 70°C L T4356IDE-2#PBF L T4356IDE-2#TRPBF 43562 12-Lead (4mm × 3mm) Plastic DFN –40°C to 85°C L T4356HDE-2#PBF L T4356HDE-2#TRPBF 43562 12-Lead (4mm × 3mm) Plastic DFN –40°C to 125°C L T4356CMS-1#PBF L T4356CMS-1#TRPBF L TCNS 10-Lead Plastic MSOP 0°C to 70°C L T4356IMS-1#PBF L T4356IMS-1#TRPBF L TCNS 10-Lead Plastic MSOP –40°C to 85°C L T4356HMS-1#PBF L T4356HMS-1#TRPBF L TCNS 10-Lead Plastic MSOP –40°C to 125°C L T4356CS-1#PBF L T4356CS-1#TRPBF L T4356S-1 16-Lead Plastic SO 0°C to 70°C L T4356IS-1#PBF L T4356IS-1#TRPBF L T4356S-1 16-Lead Plastic SO –40°C to 85°C L T4356HS-1#PBF L T4356HS-1#TRPBF L T4356S-1 16-Lead Plastic SO –40°C to 125°C L T4356CS-2#PBF L T4356CS-2#TRPBF L T4356S-2 16-Lead Plastic SO 0°C to 70°C L T4356IS-2#PBF L T4356IS-2#TRPBF L T4356S-2 16-Lead Plastic SO –40°C to 85°C L T4356HS-2#PBF L T4356HS-2#TRPBF L T4356S-2 16-Lead Plastic SO –40°C to 125°C LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE L T4356CDE-1 L T4356CDE-1#TR 43561 12-Lead (4mm × 3mm) Plastic DFN 0°C to 70°C L T4356IDE-1 L T4356IDE-1#TR 43561 12-Lead (4mm × 3mm) Plastic DFN –40°C to 85°C L T4356HDE-1 L T4356HDE-1#TR 43561 12-Lead (4mm × 3mm) Plastic DFN –40°C to 125°C L T4356CDE-2 L T4356CDE-2#TR 43562 12-Lead (4mm × 3mm) Plastic DFN 0°C to 70°C L T4356IDE-2 L T4356IDE-2#TR 43562 12-Lead (4mm × 3mm) Plastic DFN –40°C to 85°C L T4356HDE-2 L T4356HDE-2#TR 43562 12-Lead (4mm × 3mm) Plastic DFN –40°C to 125°C L T4356CMS-1 L T4356CMS-1#TR L TCNS 10-Lead Plastic MSOP 0°C to 70°C L T4356IMS-1 L T4356IMS-1#TR L TCNS 10-Lead Plastic MSOP –40°C to 85°C L T4356HMS-1 L T4356HMS-1#TR L TCNS 10-Lead Plastic MSOP –40°C to 125°C L T4356CS-1 L T4356CS-1#TR L T4356S-1 16-Lead Plastic SO 0°C to 70°C L T4356IS-1 L T4356CS-1#TR L T4356S-1 16-Lead Plastic SO –40°C to 85°C L T4356HS-1 L T4356HS-1#TR L T4356S-1 16-Lead Plastic SO –40°C to 125°C L T4356CS-2 L T4356CS-2#TR L T4356S-2 16-Lead Plastic SO 0°C to 70°C L T4356IS-2 L T4356IS-2#TR L T4356S-2 16-Lead Plastic SO –40°C to 85°C L T4356HS-2 L T4356HS-2#TR L T4356S-2 16-Lead Plastic SO –40°C to 125°C Consult L TC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container . For more information on lead free part marking, go to: http://www.linear .com/leadfree/ For more information on tape and reel specifi cations, go to: http://www.linear .com/tapeandreel/

The l denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at TA = 25°C. VCC = 12V unless otherwise noted.

ELECTRICAL CHARACTERISTICS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VCC Operating Voltage Range l 48 0 V ICC VCC Supply Current V SHDN = Float l 1 1.5 mA VSHDN = 0V , IN+ = 1.3V , L T4356-1 L T4356I-1, L T4356C-1 L T4356H-1 l l μA μA μA V SHDN = 0V , IN+ = 1.3V , L T4356-2 L T4356I-2, L T4356C-2 L T4356H-2 l l 100 250 μA μA μA I R Reverse Input Current V SNS = VCC = –30V , SHDN Open VSNS = VCC = VSHDN = –30V l l 0.3 0.8 mA mA ΔVGATE GATE Pin Output High Voltage V CC = 4V; (VGATE – VOUT) 80V ≥ VCC ≥ 8V; (VGATE – VOUT) l l 4.5 V V IGATE(UP) GATE Pin Pull-Up Current V GATE = 12V; VCC = 12V VGATE = 48V; VCC = 48V l l –4.5 –23 –30 –36 –50 μA μA IGATE(DN) GATE Pin Pull-Down Current Overvoltage, V FB = 1.4V , VGATE = 12V Overcurrent, VCC – VSNS = 120mV , VGATE = 12V Shutdown Mode, VSHDN = 0V , VGATE = 12V l l l 1.5 150 mA mA mA V FB FB Pin Servo Voltage V GATE = 12V; VOUT = 12V , L T4356I, L T4356C VGATE = 12V; VOUT = 12V , L T4356H l l 1.225 1.215 1.25 1.25 1.275 1.275 V V IFB FB Pin Input Current V FB = 1.25V l 0.3 1 μA ΔVSNS Overcurrent Fault Threshold ΔVSNS = (VCC – VSNS), VCC = 12V , L T4356I, L T4356C ΔVSNS = (VCC – VSNS), VCC = 12V , L T4356H ΔVSNS = (VCC – VSNS), VCC = 48V , L T4356I, L T4356C ΔVSNS = (VCC – VSNS), VCC = 48V , L T4356H l l l l 42.5 mV mV mV mV I SNS SNS Pin Input Current V SNS = VCC = 12V to 48V l 51 0 2 2 μ A ILEAK FL T, EN Pins Leakage Current AOUT Pin Leakage Current FL T, EN = 80V AOUT = 80V l 2.5 4.5 μA μA I TMR TMR Pin Pull-up Current V TMR = 1V , VFB = 1.5V , (VCC – VOUT) = 0.5V VTMR = 1V , VFB = 1.5V , (VCC – VOUT) = 75V VTMR = 1.3V , VFB = 1.5V VTMR = 1V , ΔVSNS = 60mV , (VCC – VOUT) = 0.5V VTMR = 1V , ΔVSNS = 60mV , (VCC – VOUT) = 80V l l l l l –1.5 –44 –3.5 –2.5 –195 –2.5 –50 –5.5 –4.5 –260 –56 –8.5 –6.5 –315 μA μA μA μA μA TMR Pin Pull-down Current V TMR = 1V , VFB = 1V , ΔVSNS = 0V l 1.5 2.2 2.7 μA VTMR TMR Pin Thresholds FL T From High to Low, VCC = 5V to 80V VGATE From Low to High, VCC = 5V to 80V l l 1.22 0.48 1.25 0.5 1.28 0.52 V V ΔVTMR Early Warning Period From FL T going Low to GATE going Low, VCC = 5V to 80V l 80 100 120 mV VIN+ IN+ Pin Threshold l 1.22 1.25 1.28 V IIN+ IN+ Pin Input Current V IN+ = 1.25V l 0.3 1 μA IOUT OUT Pin Input Current V OUT = VCC = 12V VOUT = VCC = 12V , VSHDN = 0V l l 200 300 μA mA ΔVOUT OUT Pin High Threshold ΔVOUT = VCC – VOUT; EN From Low to High l 0.25 0.5 0.7 V VSHDN SHDN Pin Threshold V CC = 12V to 48V l 0.6 0.4 1.4 1.7 2.1 V V VOL FL T, EN Pins Output Low I SINK = 2mA ISINK = 0.1mA l l 300 800 V mV AOUT Pin Output Low I SINK = 2mA ISINK = 0.1mA l l 200 400 V mV

The l denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at TA = 25°C. VCC = 12V unless otherwise noted. 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 specifi ed. 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. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VSHDN(FL T) SHDN Pin Float Voltage V CC = 12V to 48V l 0.6 1.2 2.1 V ISHDN SHDN Pin Current V SHDN = 0V l –1 –4 –8 μA tOFF(OC) Overcurrent Turn Off Delay Time GATE From High to Low, ΔVSNS = 0 → 120mV l 24 μ s tOFF(OV) Overvoltage Turn Off Delay Time GATE From High to Low, VFB = 0 → 1.5V l 0.25 1 μs TYPICAL PERFORMANCE CHARACTERISTICS ICC (Shutdown) vs VCCICC vs VCC VCC (V) ICC (μA) 20 40 60 80

4356 G01

VCC (V) ICC (μA) 200 400 600 20 40 60 80

4356 G02

Specifi cations are at VCC = 12V , TA = 25°C unless otherwise noted. ICC (Shutdown) vs VCC VCC (V) ICC (μA) 20 40 60 80

4356 G20

120 LT4356-2

IN+ = 1.3V 100 10 30 50 70 TEMPERATURE (°C) –50 ICC (μA) 100 150 200 0 50 100 125

4356 G21

–25 25 75 LT4356-2 ICC (Shutdown) vs TemperatureICC (Shutdown) vs Temperature TEMPERATURE (°C) –50 ICC (μA) 0 50 100 125

4356 G03

–25 25 75 LT4356-1

SHDN Current vs Temperature GATE Pull-Up Current vs V CC GATE Pull-Up Current vs Temperature GATE Pull-Down Current vs Temperature GATE Pull-Down Current vs Temperature ΔVGATE vs IGATE TEMPERATURE (°C) –50 ISHDN (μA) 0 50 100 125

4356 G04

–25 25 75 VSHDN = 0V VCC (V) IGATE (μA) 20 40 60 80

4356 G05

TEMPERATURE (°C) –50 IGATE (μA) 0 50 100 125

4356 G06

–25 25 75 VGATE = VOUT = 12V TEMPERATURE (°C) –50

100 IGATE(DOWN) (mA)

4356 G07

–25 25 75 OVERVOLTAGE CONDITION VFB = 1.5V TEMPERATURE (°C) –50 IGATE(DOWN) (mA) 0 50 100 125

4356 G08

–25 25 75 OVERCURRENT CONDITION ΔVSNS = 120mV IGATE (μA) ΔVGATE (V) 4 8 12 16

4356 G09

VOUT = 12V TYPICAL PERFORMANCE CHARACTERISTICS Specifi cations are at VCC = 12V , TA = 25°C unless otherwise noted. ΔVGATE vs Temperature ΔVGATE vs VCC Overvoltage TMR Current vs (VCC – VOUT) TEMPERATURE (°C) –50 0 50 100 125–25 25 75 ΔVGATE (V)

4356 G10

IGATE = –1μA VCC = 8V VCC = 4V VCC (V) 0 2 04 06 08 0

4356 G11

ΔVGATE (V) IGATE = –1μA VOUT = VCC TA = –45°C TA = 25°C TA = 130°C VCC – VOUT (V) ITMR (μA) 20 40 60 80

4356 G12

VOUT = 5V VTMR = 1V

Overcurrent TMR Current vs (VCC – VOUT) Warning Period TMR Current vs VCC TMR Pull-Down Current vs Temperature Output Low Voltage vs Current Overvoltage Turn-Off Time vs Temperature Overcurrent Turn-Off Time vs Temperature VCC – VOUT (V) ITMR (μA) 120 160 20 40 60 80

4356 G13

VOUT = 0V VTMR = 1V VCC (V) 0 2 04 06 08 0

4356 G14

ITMR (μA)

14 OVERVOLTAGE, EARLY

V FB = 1.5V VTMR = 1.3V TEMPERATURE (°C) –50 ITMR (μA) 0 50 100 125

4356 G15

3.0 2.5 2.0 1.5 1.0 0.5 –25 25 75 VTMR = 1V CURRENT (mA) VOL (V) 1.0 2.0 3.0 0.5 1.5 2.5 3.5 2.0 3.0

4356 G16

4.0 1.00.5 2.5 1.5 AOUT EN FLT TEMPERATURE (°C) –50 100 tOFF (ns) 0 50 100 125

4356 G17

–25 25 75 OVERVOLTAGE CONDITION VFB = 1.5V TEMPERATURE (°C) –50 1.0 1.5 tOFF (μs) 0 50 100 125

4356 G18

4.0 3.5 3.0 2.5 2.0 –25 25 75 OVERCURRENT CONDITION ΔVSNS = 120mV TYPICAL PERFORMANCE CHARACTERISTICS Specifi cations are at VCC = 12V , TA = 25°C unless otherwise noted. VCC (V) ICC (mA)–10 –15 –80

4356 G19

–20 –40 –60 –20 VCC = SNS Reverse Current vs Reverse Voltage

AOUT (DFN and SO Packages Only): Amplifi er Output. Open collector output of the auxiliary amplifi er . It is capable of sinking up to 2mA from 80V . The negative input of the amplifi er is internally connected to a 1.25V reference. EN: Open-Collector Enable Output. The EN pin goes high impedance when the voltage at the OUT pin is above (V CC – 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 . Exposed Pad (DFN Package Only): Exposed pad may be left open or connected to device ground (GND). 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. FL T: 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 cur- rent amplifi ers control the GATE pin to regulate the output voltage and limit the current through the MOSFET . GND: Device Ground. IN + (DFN and SO Packages Only): Positive Input of the Auxiliary Amplifi er . This amplifi er 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. 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 V CC, the EN pin goes high impedance. SHDN: Shutdown Control Input. The L T4356 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 1μA 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 amplifi er turns off in the L T4356-1 but continues operating in the L T4356-2. 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 V CC and SNS pins to 50mV . At the same time the sense amplifi er 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 V CC 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 cool down periods. The current charging up this pin during fault conditions depends on the voltage difference between the V CC and OUT pins. When VTMR reaches 1.25V , the FL T pin pulls low to indicate the detection of a fault condition. If the condition persists, the pass transistor turns off when V TMR reaches the threshold of 1.35V . As soon as the fault condition disappears, the pull up current stops and a 2μA current starts to pull the TMR pin down. When V TMR reaches the retry threshold of 0.5V , the GATE pin pulls high turning back on the pass transistor . 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 7μA with all the functional blocks off.

+ – VCC SHDN IN+ AUXILIARY AMPLIFIER IA 1.25V 50mV 2μA 1.35V 1.25V – 1.25V 0.5V SNS TMR GND GATE 14V AOUT OUT 4356 BD VCC ITMR FLT EN FB+ CHARGE PUMP CONTROL LOGIC GATEOFF FLT OUT OVOC VA SHDN RESTART

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 L T4356 is an overvoltage protection regulator that drives an external N-channel MOSFET as the pass transis- tor . 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 require- ment 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. T wo MOSFETs can be connected back to back to replace an inline Schottky diode for reverse input protection. This improves the ef- fi ciency and increases the available supply voltage level to the load circuitry during cold crank. Normally, the pass transistor is fully on, powering the loads with very little voltage drop. When the supply volt- age surges too high, the voltage amplifi er (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 capaci- tor connected at the TMR pin to ground. If the voltage at the TMR pin, V TMR, reaches 1.25V , the FL T 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 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 FL T pin will then go to a high impedance state. 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 overvolt- age, 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). The L T4356 senses an overcurrent condition by monitor- ing the voltage across an optional sense resistor placed between the V CC and SNS pins. An active current limit circuit (IA) controls the GATE pin to limit the sense volt- age 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 FL T 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 amplifi er is provided with the negative input connected to an internal 1.25V reference. The output pull down device is capable of sinking up to 2mA of current allowing it to drive an LED or opto coupler . This amplifi er can be confi gured 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 7μA for the L T4356-1. The supply current drops down to 60μA while keeping the internal reference and the auxiliary amplifi er active for the L T4356-2 version during shutdown. OPERATION

The L T4356 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 amplifi er , 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 L TC4356 limits the voltage at the OUT pin during an overvoltage situation. An internal voltage amplifi er regu- lates 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 con- nected 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 cool down 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. Overcurrent Fault The L T4356 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 V CC 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 cool down period has transpired, the GATE pin is allowed to pull back up and turn on the pass transistor . Fault Timer The L T4356 includes an adjustable fault timer pin. Con- necting 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 cool down 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(V DS), which is typically from the V CC pin to the OUT pin. This scheme takes better advantage of the available Safe Operating Area (SOA) of the MOSFET than would a fi xed timer current. The timer function operates down to V CC = 5V across the whole temperature range. APPLICATIONS INFORMATION

DS in both overvoltage and overcurrent events. Figure 1. Overvoltage Fault Timer Current Figure 2. Overcurrent Fault Timer Current

4356 F01

0.50 TIME

4356 F02

drive can be as low as 4.5V . selection of the fault timer capacitor . cause more stress on the power MOSFET . current starts to discharge the timer capacitor to ground. V(BR)DSS, the threshold voltage, and the SOA. voltage will appear across the MOSFET . Figure 3. Prototypical T ransient Waveform

4356 F03tr

type, and rises to infi nity under DC operating conditions. 2t is not the same for all combinations of I D and V DS. absorbing energy above a certain voltage. waveform is calculated as follows (Figure 4).

2 ILOAD

2 VPK –VREG()

integrating the square of MOSFET power versus time.

• CL

Figure 4. Safe Operating Area Required to Survive Prototypical

4356 F04

Figure 6. Auxiliary LDO Output with Optional Current Limit

4356 F05

4356 F06

prevent self enhancement of the N-channel MOSFET . connected to C1 as shown in Figure 5. Figure 7. Overvoltage Regulator with N-channel MOSFET

4356 F07

if no pull up device is used to help turn it on. input will clamp the voltage spikes. input of the DC/DC converter . Figure 8. Overvoltage Regulator with P-Channel MOSFET Figure 9. Overvoltage Regulator with Low-Battery Detection

4356 F08

4356 F09

To achieve accurate current sensing, Kelvin connection to the current sense resistor (RSNS in Figure 9) is recom- mended. 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 530μΩ/square. Small resistances can cause large errors in high current applications. Noise immunity will be improved signifi cantly by locating resistive dividers close to the pins with short V CC and GND traces. Design Example As a design example, take an application with the follow- ing specifi cations: 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 V OUT to 16V during an overvoltage event: VREG = 1.25V • R1 + R2() R2 = 16V Set the current through R1 and R2 during the overvoltage condition to 250μA. R2 = 1.25V 250μA = 5k Choose 4.99k for R2. 1.25V = 58.88k The closest standard value for R1 is 59k. Next calculate the sense resistor , RSNS, value: RSNS = 50mV ILIM = 50mV 5A = 10mΩ CTMR is then chosen for 1ms of early warning time: CTMR = 1ms • 5μA 100mV = 50nF The closest standard value for CTMR is 47nF . Finally, calculate R4 and R5 for the 6V low battery threshold detection: Choose 100k for 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 45.5μA = 0.878ms The power dissipation on Q1 equals to: P = 14V • 50mV 10mΩ = 70W These conditions are well within the Safe Operating Area of IRLR2908. APPLICATIONS INFORMATION

Wide Input Range 5V to 28V Hot Swap with Undervoltage Lockout CTMR 1μF 10Ω RSNS 20mΩ SUD50N03-10 VIN

4356 TA02

49.9k 118k 100μF 47nF TYPICAL APPLICATIONS 24V Overvoltage Regulator Withstands 150V at VIN CTMR 0.1μF IRF640VIN 24V VOUT CLAMPED AT 32V

4356 TA03

6 FB 2

D2* SMAT70A 4.99k 118k GATE 10Ω *DIODES INC.

Overvoltage Regulator with Undervoltage Lockout CTMR 0.1μF 10Ω RSNS 20mΩ IRLR2908 VIN

4356 TA04

4.99k 100k 280k 59k D2* SMAJ58A UV RISING = 5.04V *DIODES INC. Overvoltage Regulator with Low Battery Detection and Output Keep Alive During Shutdown 10Ω RSNS 10mΩVIN 12V VOUT 12V, 4A CLAMPED AT 16V

4356 TA05

24.9k 47k 402k 105k 294k 0.5W IRLR2908 VN2222 CTMR 0.1μF D2* SMAJ58A *DIODES INC.

2.5A, 48V Hot Swap with Overvoltage Output Regulation at 72V and UV Shutdown at 35V 1N4714 BV = 33V 6.8nF C TMR 0.1μF 10Ω RSNS 15mΩ VOUT 48V 2.5A

4356 TA06

300μF 4.02k 140k 100k 47k 4.02k 226k FDB3632 D2* SMAT70A VIN 48V *DIODES INC. 2.5A, 28V Hot Swap with Overvoltage Output Regulation at 36V and UV Shutdown at 15V 1N4700 BV = 13V 6.8nF C TMR 0.1μF 10Ω RSNS 15mΩ VOUT 28V 2.5A

4356 TA07

300μF 4.02k 113k 27k 47k 4.02k 110k FDB3632 D2* SMAT70A *DIODES INC. VIN 28V

Overvoltage Regulator with Reverse Input Protection Up to –80V CTMR 0.1μF RSNS 10mΩ IRLR2908 IRLR2908VIN 12V VOUT 12V, 3A CLAMPED AT 16V

4356 TA08

D2* SMAJ58CA 4.99k 59k GATE 10k D3** IN4148 * DIODES INC. ** OPTIONAL COMPONENT FOR REDUCED STANDBY CURRENT 2N3904 1N4148 10Ω 10Ω

12-Lead Plastic DFN (4mm × 3mm) (Reference L TC DWG # 05-08-1695 Rev D) 4.00 ±0.10 (2 SIDES) 3.00 ±0.10 (2 SIDES) NOTE: 1. DRAWING PROPOSED TO BE A VARIATION OF VERSION (WGED) IN JEDEC PACKAGE OUTLINE M0-229 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 0.40 ± 0.10 BOTTOM VIEW—EXPOSED PAD 1.70 ± 0.10 0.75 ±0.05 R = 0.115 TYP R = 0.05 TYP

2.50 REF

R = 0.20 OR 0.35 × 45° CHAMFER PIN 1 TOP MARK (NOTE 6)

0.200 REF

0.00 – 0.05 (UE12/DE12) DFN 0806 REV D RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 2.20 ±0.05 0.70 ±0.05 3.60 ±0.05 PACKAGE OUTLINE 3.30 ±0.10 0.25 ± 0.05

0.50 BSC

1.70 ± 0.05 3.30 ±0.05 0.25 ± 0.05 PACKAGE DESCRIPTION

(Reference L TC DWG # 05-08-1661) MSOP (MS) 0307 REV E 0.53 ± 0.152 (.021 ± .006) SEATING PLANE 0.18 (.007) 1.10 (.043) MAX 0.17 – 0.27 (.007 – .011) TYP 0.86 (.034) REF 0.50 (.0197) BSC 12 3 45 4.90 ± 0.152 (.193 ± .006) 0.497 ± 0.076 (.0196 ± .003) REF8910 7 6 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 3.00 ± 0.102 (.118 ± .004) (NOTE 4) 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 0.254 (.010) 0° – 6° TYP DETAIL “A” DETAIL “A” GAUGE PLANE 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 0.889 ± 0.127 (.035 ± .005) RECOMMENDED SOLDER PAD LAYOUT 0.305 ± 0.038 (.0120 ± .0015) TYP 0.50 (.0197) BSC 0.1016 ± 0.0508 (.004 ± .002) PACKAGE DESCRIPTION

16-Lead Plastic Small Outline (Narrow .150 Inch) (Reference L TC DWG # 05-08-1610) .016 – .050 (0.406 – 1.270) .010 – .020 (0.254 – 0.508)s 45o 0o – 8o TYP .008 – .010 (0.203 – 0.254) N 2 3 4 5 6 7 8 N/2 .150 – .157 (3.810 – 3.988) NOTE 3 16 15 14 13 .386 – .394 (9.804 – 10.008) NOTE 3 .228 – .244 (5.791 – 6.197) 12 11 10 9 S16 0502 .053 – .069 (1.346 – 1.752) .014 – .019 (0.355 – 0.483) TYP .004 – .010 (0.101 – 0.254) .050 (1.270) BSC .245 MIN N 1 2 3 N/2 .160 p.005 RECOMMENDED SOLDER PAD LAYOUT .045 p.005 .050 BSC .030 p.005 TYP INCHES (MILLIMETERS) NOTE: 1. DIMENSIONS IN 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)

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 representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

REVISION HISTORY

REV DATE DESCRIPTION PAGE NUMBER A 05/10 Revised Features and Description Added parameters to VOL and updated Max value for VSHDN(FL T) in the Electrical Characteristics section Revised Pin Functions section Replaced Figure 6 and made text edits in the Operation and Applications Information sections Updated drawings in the Typical Applications section 4, 5 10-17 19, 21 (Revision history begins at Rev A)

Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2009 LT 0510 REV A • PRINTED IN USA TYPICAL APPLICATION PART NUMBER DESCRIPTION COMMENTS L T1641-1/L T1641-2 Positive High Voltage Hot Swap™ Controllers Active Current Limiting, Supplies From 9V to 80V L TC1696 Overvoltage Protection Controller ThinSOT™ Package, 2.7V to 28V L TC1735 High Effi ciency Synchronous Step-Down Switching Regulator Output Fault Protection, 16-Pin SSOP L TC1778 No R SENSE™ Wide Input Range Synchronous Step-Down Controller Up to 97% Effi ciency, 4V ≤ VIN ≤ 36V , 0.8V ≤ VOUT ≤ (0.9)(VIN), IOUT Up to 20A L TC2909 T riple/Dual Inputs UV/OV Negative Monitor Pin Selectable Input Polarity Allows Negative and OV Monitoring L TC2912/L TC2913 Single/Dual UV/OV Voltage Monitor Ads UV and OV T rip Values, ±1.5% Threshold Accuracy L TC2914 Quad UV/OV Monitor For Positive and Negative Supplies L TC3727/L TC3727-1 2-Phase, Dual, Synchronous Controller 4V ≤ V IN ≤ 36V , 0.8V ≤ VOUT ≤ 14V L TC3827/L TC3827-1 Low IQ, Dual, Synchronous Controller 4V ≤ V IN ≤ 36V , 0.8V ≤ VOUT ≤ 10V , 80μA Quiescent Current L TC3835/L TC3835-1 Low IQ, Synchronous Step-Down Controller Single Channel L TC3827/L TC3827-1 L T3845 Low I Q, Synchronous Step-Down Controller 4V ≤ V IN ≤ 60V , 1.23V ≤ VOUT ≤ 36V , 120μA Quiescent Current L T3850 Dual, 550kHz, 2-Phase Sychronous Step-Down Controller Dual 180° Phased Controllers, VIN 4V to 24V , 97% Duty Cycle, 4mm × 4mm QFN-28, SSOP-28 Packages L T4256 Positive 48V Hot Swap Controller with Open-Circuit Detect Foldback Current Limiting, Open-Circuit and Overcurrent Fault Output, Up to 80V Supply L TC4260 Positive High Voltage Hot Swap Controller with ADC and I2C Wide Operating Range 8.5V to 80V L TC4352 Ideal MOSFET ORing Diode External N-channel MOSFETs Replace ORing Diodes, 0V to 18V Operation L TC4354 Negative Voltage Diode-OR Controller Controls T wo N-channel MOSFETs, 1μs Turn-Off, 80V Operation L TC4355 Positive Voltage Diode-OR Controller Controls T wo N-channel MOSFETs, 0.5μs Turn-Off, 80V Operation Hot Swap, No R SENSE and ThinSOT are trademarks of Linear Technology Corporation. Overvoltage Regulator with Linear Regulator Up to 100mA CTMR 0.1μF 10Ω RSNS 10mΩ 2N2905A VIN 12V VOUT 12V, 3A CLAMPED AT 16V 2.5V, 100mA

4356 TA09

10μF 4.99k 100k 59k 249k 249k 47nF IRLR2908 D2* SMAJ58A *DIODES INC. RELATED PARTS