LT8613 (Rev. A) - Analog Devices

1 LT86131 Rev. AFor more information FeedbackTYPICAL APPLICATION FEATURESDESCRIPTION42V, 6A Synchronous Step-Down Regulator with Current Sense and 3 A Quiescent CurrentThe LT 8613 is a compact, high efficiency, high speed synchronous monolithic step-down switching regulator that consumes only 3 A of quiescent current. Top and bottom power switches are included with all necessary circuitry to minimize the need for external components. The built-in current sense amplifier with monitor and con-trol pins allows accurate input or output current regulation and limiting. 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 com-pensation with peak current mode topology allows the use of small inductors and results in fast transient response and good loop stability.

2 The EN/UV pin has an accurate 1V threshold and can be used to program VIN undervolt-age lockout or to shut down the LT8613 reducing the input supply current to 1 A. 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 pro-grammed output voltage as well as fault conditions. The LT8613 is available in a small 28-lead 3mm 6mm QFN package with exposed pad for low thermal Step-Down Converter with 6A Output Current LimitEfficiency at 5 VOUTAPPLICATIONS nRail-to-Rail Current Sense Amplifier with Monitor nWide Input Voltage Range: to 42V nUltralow Quiescent Current Burst Mode Operation: n3 A IQ Regulating 12 VIN to nOutput Ripple < 10mVP-P nHigh Efficiency Synchronous Operation: n95% Efficiency at 3A, 5 VOUT from 12 VIN n94% Efficiency at 3A, from 12 VIN nFast Minimum Switch-On Time: 40ns nLow Dropout Under All Conditions: 250mV at 3A nAllows Use of Small Inductors nLow EMI nAdjustable and Synchronizable.

3 200kHz to nCurrent Mode Operation nAccurate 1V Enable Pin Threshold nInternal Compensation nOutput Soft-Start and Tracking nSmall Thermally Enhanced 3mm 6mm 28-Lead QFN Package nAutomotive and Industrial Supplies nGeneral Purpose Step-Down nCCCV Power SuppliesBSTVINEN/UVON OFFSYNCIMONICTRLINTVCCTR/SSRTSWLT8613 GNDPGNDISPBIASISNPG8613 FVOUT5V6A1 F100 F10 TO 42V10 F1 H8m = 700kHzL: EPCOS B82559 LOAD CURRENT (A)0 EFFICIENCY (%)6570751008524568613 TA01b6090958013fSW = 700kHzL = HVIN = 24 VVIN = 12 VAll registered trademarks and trademarks are the property of their respective owners. LT86132 Rev. AFor more information CONFIGURATIONABSOLUTE MAXIMUM RATINGSVIN, EN/UV, PG, ISP, ISN ..42 VBIAS ..25 VBST Pin Above SW , TR/SS, RT, INTVCC, IMON, ICTRL..4 VSYNC Voltage ..6 VOperating Junction Temperature Range (Note 2) LT8613E .. 40 C to 125 C LT8613I .. 40 C to 125 CStorage Temperature Range .. 65 C to 150 C(Note 1)11 TOP VIEW29 GNDUDE PACKAGE28-LEAD (3mm 6mm) PLASTIC QFN JA = 40 C/W, JC(PAD) = 5 C/WEXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB12131428272625654321 SYNCTR/SSRTEN/UVVINVINVINPGNDPGNDPGNDFBP GBIASINTVCCBSTSWSWSWSWSWICTRLIMONISNISPG NDGNDGNDGND7192021222324188910171615 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25 INFORMATIONLEAD FREE FINISHTAPE AND REELPART MARKING*PACKAGE DESCRIPTIONTEMPERATURE RANGELT8613 EUDE#PBFLT8613 EUDE#TRPBFLGHX28-Lead (3mm 6mm) Plastic QFN 40 C to 125 CLT8613 IUDE#PBFLT8613 IUDE#TRPBFLGHX28-Lead (3mm 6mm)

4 Plastic QFN 40 C to 125 CContact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF Input Quiescent CurrentVEN/UV = 0V, VSYNC = 0V 20 A AVEN/UV = 2V, Not Switching, VSYNC = 0V 20 A AVEN/UV = 2V, Not Switching, VSYNC = Current in RegulationVOUT = , VIN = 6V, Output Load = 100 A VOUT = , VIN = 6V, Output Load = 1mAl l24 23060 370 A AFeedback Reference VoltageVIN = 12V, ILOAD = 500mA VIN = 12V, ILOAD = 500mA VFeedback Voltage Line RegulationVIN = to 25V, ILOAD = Pin Input CurrentVFB = 1V Pin Current ConsumptionVBIAS = , ILOAD = 2A, 2 MHz14mALT86133 Rev. AFor 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 LT8613E 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 LT8613I is guaranteed over the full 40 C to 125 C operating junction The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25 On-TimeILOAD = 2A, SYNC = 0V ILOAD = 2A, SYNC = l20 2040 3560 55ns nsMinimum Off-Time5085120nsOscillator FrequencyRT = 221k, ILOAD = RT = , ILOAD = RT = , ILOAD = l l180 665 700 735 kHz MHzTop Power NMOS On-ResistanceISW = 1A65m Top Power NMOS Current Power NMOS On-ResistanceVINTVCC = , ISW = 1A29m Valley Current LimitVINTVCC = Leakage CurrentVIN = 42V, VSW = 0V, 42V AEN/UV Pin ThresholdEN/UV Pin Hysteresis 40mVEN/UV Pin CurrentVEN/UV = 2V 20120nAPG Upper Threshold Offset from VFBVFB Lower Threshold Offset from VFBVFB Risingl LeakageVPG = 4040nAPG Pull-Down ResistanceVPG = SYNC ThresholdSYNC Falling SYNC VSYNC Pin CurrentVSYNC = 2V 100100nATR/SS Source ATR/SS Pull-Down ResistanceFault Condition, TR/SS = Current Sense Voltage (VISP-ISN)VICTRL = , VISN = VICTRL = , VISN = 0V VICTRL = 800mV, VISN = VICTRL = 800mV, VISN = 0V VICTRL = 200mV, VISN = VICTRL = 200mV, VISN = 0Vl l l l l l48 46 38 37 5 450 41 42 10 56 46 47 15 17mV mV mV mV mV mVIMON Monitor Pin VoltageVISP-ISN = 50mV, VISN = VISP-ISN = 50mV, VISN = 0V VISP-ISN = 10mV, VISN = VISP-ISN = 10mV, VISN = 0Vl l l 130 220 320 300V V mV mVISP, ISN Pin Bias Currentl 2020 Atemperature range.

6 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. Junction temperature will exceed 150 C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature will reduce AFor more information PERFORMANCE CHARACTERISTICSE fficiency at vs FrequencyReference VoltageEN/UV Pin ThresholdsLoad RegulationLine RegulationEfficiency at 5 VOUTE fficiency at at 5 VOUTFREQUENCY (kHz)0 EFFICIENCY (%)75801009010001500200025008613 G05709585500 VOUT = = 12VL = HLOAD = 2 ATEMPERATURE ( C) VOLTAGE (V) 2535155 TEMPERATURE ( C) THRESHOLD (V) RISINGEN/UV FALLINGOUTPUT LOAD (A)0 LOAD REGULATION (%) G08 CURRENT (A)0 EFFICIENCY (%)6570751008524568613 G016090958013fSW = 700kHzL = H, EPCOS B82559 VIN = 24 VVIN = 12 VLOAD CURRENT (A)0 EFFICIENCY (%)6570751008524568613 G026090958013fSW = 700kHzL = H, EPCOS B82559 VIN = 24 VVIN = 12 VLOAD CURRENT (A) (%) = 700kHzL = HVIN = 24 VVIN = 12 VLOAD CURRENT (A) (%) = 700kHzL = HVIN = 24 VVIN = 12 VINPUT VOLTAGE (V)0 CHANGE IN VOUT (%)

7 G09 = 5 VLOAD = 1 ALT86135 Rev. AFor more information PERFORMANCE CHARACTERISTICSTop FET Current LimitMinimum On-TimeMinimum Off-TimeDropout VoltageBurst FrequencySwitching FrequencyNo Load Supply CurrentTop FET Current Limit vs Duty CycleMinimum Load to Full Frequency (SYNC Hi)INPUT VOLTAGE (V)0 INPUT CURRENT ( A) = 5 VDUTY CYCLE (%)0 TOP FET CURRENT LIMIT (A)4610820408613 G115976080100 LOAD CURRENT (mA)0 SWITCH FREQUENCY (kHz)05006008008613 G17400300200100700100200500300400 VIN = 12 VVOUT = 5VL = HINPUT VOLTAGE (V)0 MINIMUM LOAD (mA)04050608613 G183020101020503040 TEMPERATURE ( C) 50 CURRENT LIMIT (A)467119 2508613 G12510825507510012515015% DUTY CYCLE70% DUTY CYCLELOAD CURRENT (A)0 MINIMUM ON-TIME (ns)1525304518613 G1320403523456 VSYNC = 0 VVSYNC = ( C) 50 MINIMUM OFF-TIME (ns)608085100 258613 G1475706595900255075150100125 LOAD CURRENT (A)0 DROPOUT VOLTAGE (V) ( C) 50 SWITCHING FREQUENCY (kHz)6607107207408613 G16700690680670730 250255015010075125RT = AFor more information PERFORMANCE CHARACTERISTICSF requency FoldbackSoft-Start TrackingSoft-Start CurrentPG Low ThresholdsPG High ThresholdsRT Programmed Switching FrequencyVIN UVLOS witching WaveformsSwitching WaveformsFB VOLTAGE (V)0 SWITCHING FREQUENCY (kHz) = = 12 VVSYNC = 0 VRT = VOLTAGE (V)0FB VOLTAGE (V) ( C) 50SS PIN CURRENT ( A) = ( C) THRESHOLD OFFSET FROM VREF (%) 2535155FB RISINGFB FALLINGTEMPERATURE ( C) 55 THRESHOLD OFFSET FROM VREF (%) G23 2535155FB RISINGFB FALLINGSWITCHING FREQUENCY (MHz) PIN RESISTOR (k ) ( C) 55 INPUT VOLTAGE (V) s/DIV12 VIN TO 5 VOUT AT 20mA; FRONT PAGE APPVSYNC = 0V8613 G26IL1A/DIVVSW5V/DIV1 s/DIV12 VIN TO 5 VOUT AT 2 AFRONT PAGE APP8613 G27LT86137 Rev.

8 AFor more information PERFORMANCE CHARACTERISTICSS witching WaveformsTransient ResponseTransient ResponseTransient ResponseStart-Up Dropout PerformanceStart-Up Dropout PerformanceIL1A/DIVVSW10V/DIV500ns/DIV36 VIN TO 5 VOUT AT 2 AFRONT PAGE APP8613 G28 ILOAD1A/DIVVOUT200mV/DIV50 TO TRANSIENT12 VIN TO 5 VOUTCOUT = 2 47 FFRONT PAGE APP8613 G29 ILOAD1A/DIVVOUT200mV/DIV20 s/DIV1A TO 2A TRANSIENT12 VIN TO 5 VOUTCOUT = 2 47 FFRONT PAGE APP8613 G30 ILOAD1A/DIVVOUT200mV/DIV20 s/DIV1A TO 3A TRANSIENT12 VIN TO 5 VOUTCOUT = 2 47 FFRONT PAGE APP8613 G31 VIN2V/DIVVOUT2V/DIV100 LOAD(2A IN REGULATION)8613 G32 VINVOUTVIN2V/DIVVOUT2V/DIV100ms/DIV20 LOAD(250mA IN REGULATION)8613 G33 VINVOUTLT86138 Rev. AFor more information PERFORMANCE CHARACTERISTICSVISP-VISN Sense VoltageIMON VoltageVISP-VISN Sense VoltageIMON VoltageICTRL VoltageIMON VoltageICTRL VOLTAGE (mV)00 MAX VISP-VISN VOLTAGE (mV)1020304050605001000150020008613 G40 TEMPERATURE ( C) 50 MAX VISP-VISN VOLTAGE (mV)5152531508613 G4150494846050100 252575125475554 VISP = 0 VVISP = 3 VISP-ISN COMMON MODE (V)045 MAX VISP-VISN VOLTAGE (mV) (mV)00 VIMON (mV)20040060080010001200102030408613 G4350 VSYNC = (mV)00 VIMON (mV)20040060080010001200102030408613 G4450 VSYNC = 0 VISP-ISN COMMON MODE (V) VOLTAGE (V) = 50mVLT86139 Rev.

9 AFor more information FUNCTIONSSYNC (Pin 1): External Clock Synchronization Input. Ground this pin for low ripple Burst Mode operation at low output loads. Tie to a clock source for synchroniza-tion 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. When SYNC is DC high or synchronized, frequency foldback will be disabled. Do not float this (Pin 2): 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 LT8613 to regulate the FB pin to equal the TR/SS pin voltage. When TR/SS is above , the tracking function is disabled and the internal reference resumes control of the error ampli-fier. An internal A pull-up current from INTVCC on this pin allows a capacitor to program output voltage slew rate.

10 This pin is pulled to ground with an internal 230 MOSFET during shutdown and fault conditions; use a series resistor if driving from a low impedance output. This pin may be left floating if the tracking function is not (Pin 3): A resistor is tied between RT and ground to set the switching (Pin 4): The LT8613 is shut down when this pin is low and active when this pin is high. The hysteretic threshold voltage is going up and going down. Tie to VIN if the shutdown feature is not used. An external resistor divider from VIN can be used to program a VIN threshold below which the LT8613 will shut (Pins 5, 6, 7): The VIN pins supply current to the LT8613 internal circuitry and to the internal topside power switch. These pins must be tied together and be locally bypassed. Be sure to place the positive terminal of the input capacitor as close as possible to the VIN pins, and the negative capacitor terminal as close as possible to the PGND (Pins 8, 9, 10): Power Switch Ground.