LT8614 42V, 4A Synchronous Step-Down Silent Switcher with ...

1 LT86141 Rev. FFor more information FeedbackTYPICAL APPLICATION FEATURESDESCRIPTION42V, 4A Synchronous Step-Down Silent Switcher with A Quiescent CurrentThe LT 8614 Step-Down regulator features Silent Switcher architecture designed to minimize EMI emissions while delivering high efficiency at frequencies up to 3 MHz. Assembled in a 3mm 4mm QFN, the monolithic con-struction with integrated power switches and inclusion of all necessary circuitry yields a solution with a minimal PCB footprint. An ultralow A quiescent current with the output in full regulation enables applications requiring highest efficiency at very small load currents. Transient response remains excellent and output voltage ripple is below 10mVP-P at any load, from zero to full current. The LT8614 allows high VIN to low VOUT conversion at high frequency with a fast minimum top switch on-time of 30ns. Operation is safe in overload even with a saturated features are included and easy to use: An open-drain PG pin signals when the output is in regulation.

2 The SYNC pin allows clock synchronization and choice of Burst Mode operation or pulse-skipping mode. Soft-start and tracking functionality is accessed via the TR/SS pin. An accurate enable threshold can be set using the EN/UV pin and a resistor at the RT pin programs switch 4A Step-Down Converter12 VIN to 5 VOUT EfficiencyAPPLICATIONS nSilent Switcher Architecture nUltralow EMI Emissions nHigh Efficiency at High Frequency nUp to 96% Efficiency at 1 MHz, 12 VIN to 5 VOUT nUp to 94% Efficiency at 2 MHz, 12 VIN to 5 VOUT nWide Input Voltage Range: to 42V nUltralow Quiescent Current Burst Mode Operation: A IQ Regulating 12 VIN to nOutput Ripple < 10mVP-P nFast Minimum Switch On-Time: 30ns nLow Dropout Under All Conditions: 125mV at 1A nSafely Tolerates Inductor Saturation in Overload nAdjustable and Synchronizable: 200kHz to 3 MHz nPeak Current Mode Operation nAccurate 1V Enable Pin Threshold nInternal Compensation nOutput Soft-Start and Tracking nSmall 18-Lead 3mm 4mm QFN nAEC-Q100 Qualified for Automotive Applications nAutomotive and Industrial Supplies nGeneral Purpose Step-Down nGSM Power SuppliesVIN2 VIN1EN/UVPGLT86148614 TA01aBSTSYNC/MODESWTR/SSBIASINTVCCFBRTGN D1 F1 MVOUT5V4A1 TO H243kGND2 GND1fSW = 1 MHzLOAD CURRENT (A)0 EFFICIENCY (%) registered trademarks and trademarks are the property of their respective owners.

3 Protected by patents, including more information FPIN CONFIGURATIONABSOLUTE MAXIMUM RATINGSVIN, EN/UV, PG ..42 VBIAS ..30 VBST Pin Above SW , TR/SS, RT, INTVCC ..4 VSYNC/MODE Voltage ..6 VOperating Junction Temperature Range (Note 2) LT8614E .. 40 C to 125 C LT8614I .. 40 C to 125 C LT8614H .. 40 C to 150 C LT8614MP OBSOLETE .. 55 C to 150 CStorage Temperature Range .. 65 C to 150 C(Note 1)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 RANGELT8614 EUDC#PBFLT8614 EUDC#TRPBFLGGQ18-Lead (3mm 4mm) Plastic QFN 40 C to 125 CLT8614 IUDC#PBFLT8614 IUDC#TRPBFLGGQ18-Lead (3mm 4mm) Plastic QFN 40 C to 125 CLT8614 HUDC#PBFLT8614 HUDC#TRPBFLGGQ18-Lead (3mm 4mm) Plastic QFN 40 C to 150 COBSOLETELT8614 MPUDC#PBFLT8614 MPUDC#TRPBFLGGQ18-Lead (3mm 4mm) Plastic QFN 55 C to 150 CAUTOMOTIVE PRODUCTS** LT8614 EUDC#WPBFLT8614 EUDC#WTRPBFLGGQ18-Lead (3mm 4mm) Plastic QFN 40 C to 125 CLT8614 IUDC#WPBFLT8614 IUDC#WTRPBFLGGQ18-Lead (3mm 4mm)

4 Plastic QFN 40 C to 125 CLT8614 HUDC#WPBFLT8614 HUDC#WTRPBFLGGQ18-Lead (3mm 4mm) Plastic QFN 40 C to 150 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 suffix.**Versions of this part are available with controlled manufacturing to support the quality and reliability requirements of automotive applications. These models are designated with a #W suffix. Only the automotive grade products shown are available for use in automotive applications. Contact your local analog Devices account representative for specific product ordering information and to obtain the specific Automotive Reliability reports for these Input Quiescent CurrentVEN/UV = 0V 8 A AVEN/UV = 2V, Not Switching, VSYNC = 0V 10 A AVEN/UV = 2V, Not Switching, VSYNC = VIEWUDC PACKAGE18-LEAD (3mm 4mm) PLASTIC QFN JA = 40 C/W, JC(PAD) = 12 C/W (Note 3)EXPOSED PAD (PINS 21, 22) ARE SW, SHOULD BE SOLDERED TO PCBNOTE: PINS 5, 12 ARE REMOVED.

5 CONFIGURATION DOES NOT MATCH JEDEC 20-PIN PACKAGE OUTLINE1 BIASINTVCCBSTVIN1 GND1TR/SSRTEN/UVVIN2 GND2 GND1 SWSWGND2 FBPGGNDSYNC/MODE1615141311234621SW22 SWLT86143 Rev. FFor 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 LT8614E is guaranteed to meet performance specifications from 0 C to 125 C junction temperature. Specifications over the 40 C to 125 C operating junction temperature range are assured by design, characterization, and correlation with statistical process controls. The LT8614I is guaranteed over the full 40 C to 125 C operating junction temperature range. The LT8614H is guaranteed to meet performance specifications from 40 C to 150 C operating junction temperature range. The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25 junction temperatures degrade operating lifetimes.

6 Operating lifetime is derated at junction temperatures greater than 125 C. Note 3: values determined per JEDEC 51-7, 51-12. See the Applications Information section for information on improving the thermal resistance. Note 4: 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 Current in RegulationVOUT = , VIN = 6V, Output Load = 100 A VOUT = , VIN = 6V, Output Load = 1mAl l21 21050 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, 2 MHz9mAMinimum On-TimeILOAD = , SYNC = 0V ILOAD = , SYNC = l15 1530 3045 45ns nsMinimum Off-Time80110nsOscillator FrequencyRT = 221k, ILOAD = 1A RT = , ILOAD = 1A RT = , ILOAD = 1Al l l180 665 700 735 kHz MHzTop Power NMOS On-ResistanceISW = 1A85m Top Power NMOS Current Power NMOS On-ResistanceVINTVCC = , ISW = 1A40m Bottom Power NMOS Current LimitVINTVCC = Leakage CurrentVIN = 42V, VSW = 0V.

7 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 4040nATR/SS Source ATR/SS Pull-Down ResistanceFault Condition, TR/SS = LT86144 For more information FTYPICAL PERFORMANCE CHARACTERISTICSE fficiency at vs FrequencyBurst Mode Efficiency vs Inductor ValueReference VoltageEN Pin ThresholdsLoad RegulationEfficiency at 5 VOUTE fficiency at at 5 VOUTLOAD CURRENT (A)050 EFFICIENCY (%) = 12 VVIN = 24 VVIN = 36 VfSW = 1 MHzL = HLOAD CURRENT (A)050 EFFICIENCY (%)5565707510085128614 = 12 VVIN = 24 VVIN = 36 VfSW = 1 MHzL = HLOAD CURRENT (mA) (%)5060708011010010008614 G03302010090100 VIN = 12 VVIN = 24 VVIN = 36 VfSW = 1 MHzL = HLOAD CURRENT (mA) (%)5060708011010010008614 G04302010090100 VIN = 12 VVIN = 24 VVIN = 36 VfSW = 1 MHzL = HSWITCHING FREQUENCY (MHz) (%)VOUT = 5 VILOAD = 1AL = HVIN = 12 VVIN = 24 VINDUCTOR VALUE ( H)065 EFFICIENCY (%)70758085909524688614 G0610 VOUT = 5 VILOAD = 10mAVIN = 12 VVIN = 24 VTEMPERATURE ( C) 50 REFERENCE VOLAGE (V) ( C) 50EN THRESHOLD (V) RISINGEN FALLINGLOAD CURRENT (A)0 IN VOUT (%) = 5 VVIN = 12 VLT86145 Rev.

8 FFor more information PERFORMANCE CHARACTERISTICSTop FET Current Limit vs Duty CycleTop FET Current LimitBottom FET Current LimitSwitch DropMinimum On-TimeSwitch DropLine RegulationNo-Load Supply CurrentNo-Load Supply CurrentINPUT VOLTAGE (V)5 IN VOUT (%) G10 = 5 VILOAD = 1 AINPUT VOLTAGE (V)00 INPUT CURRENT ( A) = REGULATIONTEMPERATURE ( C) 55 250 INPUT CURRENT ( A)1025565958614 G125201535125155 VOUT = = 12 VIN REGULATIONTEMPERATURE ( C) 50 CURRENT LIMIT (A) LIMIT (A) ( C) LIMIT (A) 25751258614 DCTEMPERATURE ( C) 50 SWITCH DROP (mV)1001501508614 G16500050100 2525751252007512525175 SWITCH CURRENT = 1 ATOP SWITCHBOTTOM SWITCHSWITCH CURRENT (A)00 SWITCH DROP (mV)50150200250500350128614 G1710040045030034 TOP SWITCHBOTTOM SWITCHTEMPERATURE ( C) 5020 MINIMUM ON-TIME (ns)222628304034050751008614 G1824363832 2525125 ILOAD = 1A, VSYNC = 0 VILOAD = 1A, VSYNC = 3 VILOAD = 2 AILOAD = 4 ALT86146 For more information FTYPICAL PERFORMANCE CHARACTERISTICSD ropout VoltageSwitching FrequencyBurst FrequencyFrequency FoldbackMinimum Load to Full Frequency (SYNC DC High)Soft-Start TrackingSoft-Start CurrentPG High ThresholdsPG Low ThresholdsLOAD CURRENT (A)0 DROPOUT VOLTAGE (mV)40060048614 ( C) 50 SWITCHING FREQUENCY (kHz)730258614 G20700680 25050670660740RT = CURRENT (mA)00 SWITCHING FREQUENCY (kHz)20040060080010001200501001502008614 G21 FRONT PAGE APPLICATIONVIN = 12 VVOUT = 5 VINPUT VOLTAGE (V)5 LOAD CURRENT (mA)60801002030458614 G22402001015253540 FRONT PAGE APPLICATIONVOUT = 5 VfSW = 1 MHzFB 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 (%) 2525150125FB RISINGFB FALLINGTEMPERATURE ( C)

9 50 THRESHOLD OFFSET FROM VREF (%) G27 2525150FB RISINGFB FALLINGLT86147 Rev. FFor more information PERFORMANCE CHARACTERISTICSRT Programmed Switching FrequencyVIN UVLOBias Pin CurrentBias Pin CurrentSwitching Waveforms, Full Frequency Continuous OperationTransient Response; Load Current Stepped from 1A to 2 ATransient Response; Load Current Stepped from 100mA (Burst Mode Operation) to Waveforms, Burst Mode OperationSwitching WaveformsSWITCHING FREQUENCY (MHz) PIN RESISTOR (k ) ( C) 55 INPUT VOLTAGE (V) VOLTAGE (V)5 BIAS PIN CURRENT (mA) = 5 VVOUT = 5 VILOAD = 1 AfSW = 700kHzSWITCHING FREQUENCY (MHz) PIN CURRENT (mA)VBIAS = 5 VVOUT = 5 VVIN = 12 VILOAD = 1 AIL500mA/DIVVSW5V/DIVVOUT5mV/DIV500ns/DI VFRONT PAGE APPLICATION12 VIN TO 5 VOUT AT 1A8614 G32IL500mA/DIVVSW5V/DIVVOUT10mV/DIV5 s/DIVFRONT PAGE APPLICATION12 VIN TO 5 VOUT AT 10mAVSYNC = 0V8614 G33IL500mA/DIVVSW5V/DIV200ns/DIVFRONT PAGE APPLICATION36 VIN TO 5 VOUT AT 1A8614 G34 ILOAD1A/DIVVOUT100mV/DIV50 s/DIVFRONT PAGE APPLICATION1A TO 2A TRANSIENT12 VIN, 5 VOUTCOUT = 47 F8614 G35 ILOAD1A/DIVVOUT200mV/DIV50 s/DIVFRONT PAGE APPLICATION100mA (Burst Mode OPERATION) TO TRANSIENT12 VIN, 5 VOUTCOUT = 47 F8614 G36LT86148 For more information FFREQUENCY (MHz)0 AMPLITUDE (dB V/m)

10 3040508002010010020030040050060070090010 00 FREQUENCY (MHz)DC2019A DEMO BOARD (WITH EMI FILTER INSTALLED) 14 VIN TO 5 VOUT AT 4A, fSW = 2 MHz0 AMPLITUDE (dB V/m)3040508008614 G39201001002003004005006007009001000 VERTICAL POLARIZATIONHORIZONTIAL POLARIZATIONLT8614 CLASS 5 PEAKLT8614 CLASS 5 PEAKTYPICAL PERFORMANCE CHARACTERISTICSS tart-Up Dropout PerformanceRadiated EMI Performance (CISPR25 Radiated Emission Test with Class 5 Peak Limits)Start-Up Dropout PerformanceVIN2V/DIVVOUT2V/DIV100 LOAD(2A IN REGULATION)8614 G37 VINVOUTVIN2V/DIVVOUT2V/DIV100ms/DIV20 LOAD(250mA IN REGULATION)8614 G38 VINVOUTLT86149 Rev. FFor more information FUNCTIONSBIAS (Pin 1): The internal regulator will draw current from BIAS instead of VIN when BIAS is tied to a voltage higher than For output voltages of to 30V this pin should be tied to VOUT. If this pin is tied to a supply other than VOUT use a 1 F local bypass capacitor on this pin. If no supply is available, tie to (Pin 2): Internal Regulator Bypass Pin.