LT8612 (Rev. B)

1 LT86121 Rev. BFor more information FeedbackTYPICAL APPLICATION FEATURESDESCRIPTION42V, 6A Synchronous Step-Down Regulator with 3 A Quiescent CurrentThe LT 8612 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. 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 cur-rent 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 undervoltage lockout or to shut down the LT8612 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 programmed output voltage as well as fault conditions. The LT8612 is available in a small 3mm 6mm 28-lead QFN package with exposed pad for low thermal 6A Step-Down ConverterEfficiency at 5 VOUTAPPLICATIONSn Wide Input Voltage Range: to 42Vn Ultralow Quiescent current Burst Mode Operation: n3 A IQ Regulating 12 VIN to nOutput Ripple < 10mVP-P n high Efficiency Synchronous Operation: n95% Efficiency at 3A, 5 VOUT from 12 VIN n94% Efficiency at 3A, from 12 VIN n Fast Minimum Switch-On-Time: 40nsn Low Dropout Under All Conditions: 250mV at 3An Allows Use of Small Inductorsn Safely Tolerates Inductor Saturation in Overload Conditionsn Adjustable and Synchronizable.

3 200kHz to current Mode Operationn Accurate 1V Enable Pin Thresholdn Internal Compensationn Output Soft-Start and Trackingn Small Thermally Enhanced 3mm 6mm 28-Lead QFN Packagen AEC-Q100 Qualified for Automotive Applicationsn Automotive and Industrial Suppliesn General Purpose Step-Downn GSM power SuppliesBSTVINEN/UVPGSYNCINTVCCTR/SSRTSW LT8612 GNDPGNDBIAS8612 FVOUT5V6A10 TO 42V1 H1M243kfSW = 700kHzL: EPCOS F1210 LOAD current (A)0 EFFICIENCY (%)6570751008524568612 TA01b6090958013fSW = 700kHzL = HVIN = 24 VVIN = 12 VAll registered trademarks and trademarks are the property of their respective BFor more information CONFIGURATIONABSOLUTE MAXIMUM RATINGSVIN, EN/UV, PG ..42 VBIAS ..25 VFB, TR/SS ..4 VSYNC Voltage.

4 6 VOperating Junction Temperature Range (Note 2) LT8612E .. 40 C to 125 C LT8612I .. 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 PCB12131428 27 26 25654321 SYNCTR/SSRTEN/UVVINVINVINPGNDPGNDPGNDFBP GBIASINTVCCBSTSWSWSWSWSWNCNCNCNCGNDGNDGN DGND7192021222324188910171615 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 RANGELT8612 EUDE#PBFLT8612 EUDE#TRPBFLGHW28-Lead (3mm 6mm)

5 Plastic QFN 40 C to 125 CLT8612 IUDE#PBFLT8612 IUDE#TRPBFLGHW28-Lead (3mm 6mm) Plastic QFN 40 C to 125 CAUTOMOTIVE PRODUCTS** LT8612 EUDE#WPBFLT8612 EUDE#WTRPBFLGHW28-Lead (3mm 6mm) Plastic QFN 40 C to 125 CLT8612 IUDE#WPBFLT8612 IUDE#WTRPBFLGHW28-Lead (3mm 6mm) 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 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.

6 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, VSYNC = 0V 20 A AVEN/UV = 2V, Not Switching, VSYNC = 0V 20 A AVEN/UV = 2V, Not Switching, VSYNC = BFor 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 LT8612E is guaranteed to meet performance specifications from 0 C to 125 C junction temperature.

7 Specifications over the 40 C to 125 C operating junction temperature range are assured by design, characterization, and correlation with statistical process controls. The LT8612I is guaranteed over the full 40 C to 125 C operating junction temperature range. high junction temperatures degrade operating lifetimes. Operating lifetime is derated at junction temperatures greater than 125 C. The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25 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 VoltageILOAD = 0mA, VBIAS = 0V ILOAD = 0mA, VBIAS = VINTVCC Undervoltage Pin current ConsumptionVBIAS =.

8 ILOAD = 2A, 2 MHz14mAMinimum 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 Bottom power NMOS 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 4040nATR/SS Source ATR/SS Pull-Down ResistanceFault Condition, TR/SS = Note 3: This IC includes overtemperature protection that is intended to protect the device during overload conditions.

9 Junction temperature will exceed 150 C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature will reduce BFor more information PERFORMANCE CHARACTERISTICSE fficiency at vs FrequencyReference VoltageEN/UV Pin ThresholdsLoad RegulationLine RegulationEfficiency at 5 VOUTE fficiency at at 5 VOUTTEMPERATURE ( C) VOLTAGE (V) 2535155 LOAD current (A) (%) = 700kHzL = HVIN = 24 VVIN = 12 VINPUT VOLTAGE (V)0 CHANGE IN VOUT (%) G09 = 5 VLOAD = 1 ATEMPERATURE ( C) THRESHOLD (V) 25100 RISINGEN/UV FALLINGOUTPUT LOAD (A)0 LOAD REGULATION (%) G08 current (A)0 EFFICIENCY (%)6570751008524568612 G016090958013fSW = 700kHzL = H, EPCOS B82559 VIN = 24 VVIN = 12 VFREQUENCY (kHz)0 EFFICIENCY (%)

10 75801009010001500200025008612 G05709585500 VOUT = = 12VL = HLOAD = 2 ALOAD current (A) (%) = 700kHzL = HVIN = 24 VVIN = 12 VLOAD current (A)0 EFFICIENCY (%)6570751008524568612 G026090958013fSW = 700kHzL = H, EPCOS B82559 VIN = 24 VVIN = 12 VLT86125 Rev. BFor 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)DUTY CYCLE (%)0 TOP FET current LIMIT (A)4610820408612 G115976080100 TEMPERATURE ( C) 50 current LIMIT (A)467119 2508612 G125108255075100 125 15015% DUTY CYCLE70% DUTY CYCLELOAD current (A)0 MINIMUM ON-TIME (ns)1525304518612 G1320403523456 VSYNC = 0 VVSYNC = ( C) 50 SWITCHING FREQUENCY (kHz)6607107207408612 G16700690680670730 250255015010075125RT = VOLTAGE (V)0 MINIMUM LOAD (mA)04050608612 G183020101020503040 INPUT VOLTAGE (V)0 INPUT current ( A)