LT8620 - 65V, 2A Synchronous Step-Down Regulator with 2 ...

1 LT862018620faFor more information CURRENT (A)0 EFFICIENCY (%) = 12 VVIN = 24 VfSW = 700kHzTYPICAL APPLICATION FEATURESDESCRIPTION65V, 2A Synchronous Step-Down Regulator with A Quiescent CurrentThe LT 8620 is a compact, high efficiency, high speed Synchronous monolithic Step-Down switching Regulator that accepts a wide input voltage range up to 65V, and consumes only A of quiescent current. Top and bottom power switches are included with all necessary circuitry to minimize the need for external components. Low ripple Burst Mode operation enables high efficiency down to very low output currents while keeping the output ripple below 10mVP-P. A SYNC pin allows synchronization to an external clock. Internal compensation with peak current mode topology allows the use of small inductors and results in fast transient response and good loop stability. The EN/UV pin has an accurate 1V threshold and can be used to program VIN undervoltage lockout or to shut down the LT8620 reducing the input supply current to 1 A.

2 A capacitor on the TR/SS pin programs the output voltage ramp rate during start-up. The PG flag signals when VOUT is within 9% of the programmed output voltage as well as fault conditions. The LT8620 is available in small 16-Lead MSOP and 3mm 5mm QFN packages with exposed pads for low thermal 2A Step-Down ConverterEfficiency at 5 VOUTAPPLICATIONS nWide Input Voltage Range: to 65V nUltralow Quiescent Current Burst Mode Operation: A IQ Regulating 12 VIN to nOutput Ripple < 10mVP-P nHigh Efficiency Synchronous Operation: n94% Efficiency at 1A, 12 VIN to 5 VOUT n92% Efficiency at 1A, 12 VIN to nFast 30ns Minimum Switch-On Time nLow Dropout Under All Conditions: 250mV at 1A nSafely Tolerates Inductor Saturation in Overload nLow EMI nAdjustable and Synchronizable: 200kHz to nAccurate 1V Enable Pin Threshold nInternal Compensation nOutput Soft-Start and Tracking nSmall Thermally Enhanced 16-Lead MSOP and 24-Lead 3mm 5mm QFN Packages nAutomotive and Industrial Supplies nGeneral Purpose Step-Down nGSM Power SuppliesL, LT , LT C, LT M, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation.

3 All other trademarks are the property of their respective TO 65V1 H1M243kfSW = FLT862028620faFor more information CONFIGURATIONABSOLUTE MAXIMUM RATINGSVIN, EN/UV ..65 VPG ..42 VBIAS ..25 VBST Pin Above SW , TR/SS, RT, INTVCC ..4V(Note 1)12345678 SYNCTR/SSRTEN/UVVINVINNCGND1615141312111 09 FBPGBIASINTVCCBSTSWSWSWTOP VIEW17 GNDMSE PACKAGE16-LEAD PLASTIC MSOP JA = 40 C/W, JC(PAD) = 10 C/W EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB24232221910 TOP VIEW25 GNDUDD PACKAGE24-LEAD (3mm 5mm) PLASTIC QFN1112654321151617181920 SYNCTR/SSRTEN/UVVINVINNCGNDFBPGBIASINTVC CBSTSWSWSWNCNCNCNCGNDNCNCNC147138 JA = 46 C/W, JC(PAD) = 5 C/W EXPOSED PAD (PIN 25) IS GND, MUST BE SOLDERED TO PCBORDER INFORMATIONLEAD FREE FINISHTAPE AND REELPART MARKING*PACKAGE DESCRIPTIONTEMPERATURE RANGELT8620 EMSE#PBFLT8620 EMSE#TRPBF862016-Lead Plastic MSOP 40 C to 125 CLT8620 IMSE#PBFLT8620 IMSE#TRPBF862016-Lead Plastic MSOP 40 C to 125 CLT8620 HMSE#PBFLT8620 HMSE#TRPBF862016-Lead Plastic MSOP 40 C to 150 CLT8620 MPMSE#PBFLT8620 MPMSE#TRPBF862016-Lead Plastic MSOP 55 C to 150 CLT8620 EUDD#PBFLT8620 EUDD#TRPBFLGGV24-Lead (3mm 5mm)

4 Plastic QFN 40 C to 125 CLT8620 IUDD#PBFLT8620 IUDD#TRPBFLGGV24-Lead (3mm 5mm) Plastic QFN 40 C to 125 CConsult LT C Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping LT C Marketing for information on non-standard lead based finish more information on lead free part marking, go to: For more information on tape and reel specifications, go to: Voltage ..6 VOperating Junction Temper atur e Range (Note 2) LT8620E .. 40 C to 125 C LT8620I .. 40 C to 125 C LT8620H .. 40 C to 150 C LT8620MP .. 55 C to 150 CStorage Temper atur e Range .. 65 C to 150 CLT862038620faFor more information CHARACTERISTICSNote 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 2: The LT8620E is guaranteed to meet performance specifications from 0 C to 125 C junction temperature.

5 Specifications over the 40 C to 125 C operating junction temperature range are assured by design, characterization, and correlation with statistical process controls. The LT8620I is guaranteed over the full 40 C to 125 C operating junction temperature range. The LT8620H is guaranteed over the full 40 C to The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25 Input Quiescent CurrentVEN/UV = 0V, VSYNC = 0V 8 A AVEN/UV = 2V, Not Switching, VSYNC = 0V 10 A AVEN/UV = 2V, Not Switching, VSYNC = Current in RegulationVOUT = , VIN = 6V, Output Load = 100 A VOUT = , VIN = 6V, Output Load = 1mAl l20 20050 350 A AFeedback Reference VoltageVIN = 6V, ILOAD = VIN = 6V, ILOAD = VFeedback Voltage Line RegulationVIN = to 42V, ILOAD = Pin Input CurrentVFB = 1V 2020nAINTVCC VoltageILOAD = 0mA, VBIAS = 0V ILOAD = 0mA, VBIAS = VINTVCC Undervoltage Pin Current ConsumptionVBIAS = , ILOAD = 1A, On-TimeILOAD = 1A, SYNC = 0V ILOAD = 1A, SYNC = l 30 3045 45ns nsMinimum Off-Time90130nsOscillator FrequencyRT = 221k, ILOAD = 1A RT =.

6 ILOAD = 1A RT = , ILOAD = 1Al l l180 665 700 735 kHz MHzTop Power NMOS On-ResistanceISW = 1A175m Top Power NMOS Current Power NMOS On-ResistanceVINTVCC = , ISW = 1A85m Bottom Power NMOS Current LimitVINTVCC = Leakage CurrentVIN = 42V, VSW = 0V, 42V AEN/UV Pin ThresholdEN/UV Pin Hysteresis 40mVEN/UV Pin CurrentVEN/UV = 2V 2020nAPG Upper Threshold Offset from VFBVFB Lower Threshold Offset from VFBVFB Risingl 6 12%PG LeakageVPG = 4040nAPG Pull-Down ResistanceVPG = SYNC ThresholdSYNC Falling SYNC VSYNC Pin CurrentVSYNC = 6V 100100nATR/SS Source ATR/SS Pull-Down ResistanceFault Condition, TR/SS = 150 C operating junction temperature range. The LT8620MP is 100% tested and guaranteed over the full 55 C to 150 C operating junction temperature range. High junction temperatures degrade operating lifetimes. Operating lifetime is derated at junction temperatures greater than 125 3: This IC includes overtemperature protection that is intended to protect the device during overload conditions.

7 Junction temperature will exceed 150 C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature will reduce more information PERFORMANCE CHARACTERISTICSE fficiency at vs Frequency at 1 AReference VoltageEN Pin ThresholdsLoad RegulationLine RegulationEfficiency at 5 VOUTE fficiency at at 5 VOUTLOAD CURRENT (A)0 EFFICIENCY (%) = 48 VVIN = 36 VVIN = 24 VVIN = 12 VfSW = 700kHzL = IHLP2525CZ-01, HLOAD CURRENT (A)0 EFFICIENCY (%) = 48 VVIN = 36 VVIN = 24 VVIN = 12 VfSW = 700kHzL = IHLP2525CZ-01, HLOAD CURRENT (mA)30 EFFICIENCY (%) = 48 VVIN = 36 VVIN = 24 VVIN = 12 VfSW = 700kHzL = IHLP2525CZ-01, HLOAD CURRENT (mA)30 EFFICIENCY (%) = 48 VVIN = 36 VVIN = 24 VVIN = 12 VfSW = 700kHzL = IHLP2525CZ-01, HSWITCHING FREQUENCY (MHz) (%)VIN = 12 VVIN = 24 VVOUT = = IHLP2525CZ-01, HTEMPERATURE ( C) VOLTAGE (V) 1258620 25050150 TEMPERATURE ( C) THRESHOLD (V)

8 25100 RISINGEN FALLINGLOAD CURRENT (A)0 IN VOUT (%) = 5 VVIN = 12 VINPUT VOLTAGE (V)5 CHANGE IN VOUT (%) G09 = 5 VILOAD = 1 ATA = 25 C, unless otherwise more information PERFORMANCE CHARACTERISTICSTop FET Current Limit vs Duty CycleTop FET Current LimitBottom FET Current LimitSwitch DropMinimum On-TimeSwitch DropNo Load Supply CurrentINPUT VOLTAGE (V)00 INPUT CURRENT ( A) = REGULATIONDUTY CYCLE0 CURRENT LIMIT (A) ( C) 5020 MINIMUM ON-TIME (ns)22243428050751008620 G16303226 2525125 ILOAD = 1A, VSYNC = 0 VILOAD = 1A, VSYNC = 3 VILOAD = 2A, VSYNC = 0 VILOAD = 2A, VSYNC = 3 VTEMPERATURE ( C) 50 250 SWITCH DROP (mV)200150350050758620 G145010030025025100125 TOP SWITCHBOTTOM SWITCHSWITCH CURRENT = 1 ASWITCH CURRENT (A) DROP (mV) SWITCHBOTTOM SWITCHTA = 25 C, unless otherwise VoltageSwitching FrequencyLOAD CURRENT (A)0 DROPOUT VOLTAGE (mV)4008620 ( C) 50 SWITCHING FREQUENCY (kHz)730508620 G18700680 2525075670660740RT = 125 150 DUTY CYCLE = 5%TEMPERATURE ( C) 55 LIMIT (A)8620 G12 TEMPERATURE ( C) 55 LIMIT (A)8620 G13LT862068620faFor more information PERFORMANCE CHARACTERISTICSRT Programmed Switching FrequencyVIN UVLOB urst FrequencyFrequency FoldbackMinimum Load to Full Frequency (SYNC DC High)Soft-Start TrackingSoft-Start CurrentPG High ThresholdsPG Low ThresholdsLOAD CURRENT (mA)0 SWITCHING FREQUENCY (kHz)4005006002008620 G19300200050100150100800 VIN = 12 VVOUT = 5V700FB VOLTAGE (V)0 SWITCHING FREQUENCY (kHz) = = 12 VVSYNC = 0 VRT = VOLTAGE (V)0FB VOLTAGE (V) = ( C) 55 PIN CURRENT ( A)8620 G23 TEMPERATURE ( C) THRESHOLD OFFSET FROM VREF (%) 1258620 2550150FB RISINGFB FALLINGTEMPERATURE ( C) 50 THRESHOLD OFFSET FROM VREF (%)

9 1258620 G25 252550150FB RISINGFB FALLINGSWITCHING FREQUENCY (MHz) PIN RESISTOR (k ) ( C) 55 INPUT VOLTAGE (V) VOLTAGE (V)LOAD CURRENT (mA)6080100152555658620 G204020053545 VOUT = 5 VfSW = 700kHzTA = 25 C, unless otherwise more information PERFORMANCE CHARACTERISTICSBias Pin CurrentBias Pin CurrentSwitching Waveforms, Full Frequency Continuous OperationSwitching Waveforms, Burst Mode OperationSwitching WaveformsTransient Response; Load Current Stepped from 1A to 2A INPUT VOLTAGE (V)5 BIAS PIN CURRENT (mA) = 5 VVOUT = 5 VILOAD = 1 AfSW = 700kHzSWITCHING FREQUENCY (MHz)00 BIAS PIN CURRENT (mA) = 5 VVOUT = 5 VVIN = 12 VILOAD = 1 AIL1A/DIVVSW5V/DIV500ns/DIV12 VIN TO 5 VOUT AT 1A8620 G30IL200mA/DIVVSW5V/DIV2 s/DIV12 VIN TO 5 VOUT AT 10mAVSYNC = 0V8620 G31IL1A/DIVVSW20V/DIV500ns/DIV48 VIN TO 5 VOUT AT 1A8620 G32 ILOAD1A/DIVVOUT100mV/DIV50 s/DIV1A TO 2A TRANSIENT12 VIN, 5 VOUTCOUT = 47 F8620 G33TA = 25 C, unless otherwise Response.

10 Load Current Stepped from 50mA (Burst Mode Operation) to 1 AILOAD1A/DIVVOUT200mV/DIV50 s/DIV50mA (Burst Mode Operation) TO 1A TRANSIENT12 VIN, 5 VOUTCOUT = 47 F8620 G34 Start-Up Dropout PerformanceVIN2V/DIVVOUT2V/DIV100 LOAD(2A IN REGULATION)8620 G35 VINVOUTS tart-Up Dropout PerformanceVIN2V/DIVVOUT2V/DIV100ms/DIV2 0 LOAD(250mA IN REGULATION)8620 G36 VINVOUTLT862088620faFor more information FUNCTIONSSYNC: External Clock Synchronization Input. Ground this pin for low ripple Burst Mode operation at low output loads. Tie to a clock source for synchronization to an external frequency. Apply a DC voltage of 3V or higher or tie to INTVCC for pulse-skipping mode. When in pulse-skipping mode, the IQ will increase to several hundred A. Do not float this : Output Tracking and Soft-Start Pin. This pin allows user control of output voltage ramp rate during start-up. A TR/SS voltage below forces the LT8620 to regulate the FB pin to equal the TR/SS pin voltage.