LTC3786 Low IQ Synchronous Boost Controller - analog.com

1 LTC378613786fcFor more information APPLICATION FEATURESDESCRIPTIONLow IQ Synchronous Boost ControllerThe LT C 3786 is a high performance Synchronous Boost converter Controller that drives all N-channel power MOSFETs. Synchronous rectification increases efficiency, reduces power losses and eases thermal requirements, allowing the LTC3786 to be used in high power Boost to 38V input supply range encompasses a wide range of system architectures and battery chemistries. When biased from the output of the Boost converter or another auxiliary supply, the LTC3786 can operate from an input supply as low as after start-up. The 55 A no-load quiescent current extends operating run time in battery-powered operating frequency can be set for a 50kHz to 900kHz range or synchronized to an external clock using the internal PLL.

2 The LTC3786 also features a precision reference and a power good output indicator. The SS pin ramps the output voltage during start-up. The PLLIN/MODE pin selects among Burst Mode operation, pulse-skipping mode or continuous inductor current mode at light to 24V/5A Synchronous Boost ConverterAPPLICATIONSn Synchronous Operation For Highest Efficiency and Reduced Heat Dissipationn Wide VIN Range: to 38V (40V Abs Max) and Operates Down to After Start-Up n Output Voltages Up to 60Vn 1% Reference Voltagen RSENSE or Inductor DCR Current Sensingn 100% Duty Cycle Capability for Synchronous MOSFETn Low Quiescent Current: 55 An Phase-Lockable Frequency (75kHz to 850kHz)n Programmable Fixed Frequency (50kHz to 900kHz)n Adjustable Output Voltage Soft-Startn Power Good Output Voltage Monitorn Low Shutdown Current IQ: <8 An Internal LDO for Gate Drive Supplyn Thermally Enhanced 16-Pin 3mm 3mm QFN and MSOP Packagesn Industrial and Automotive Power Suppliesn Automotive Start-Stop Systemsn Medical Devicesn High Voltage Battery-Powered SystemsAll registered trademarks and trademarks are the property of their respective owners.

3 SENSE+VBIASSENSE F15nF220 F220 F3786 FVIN TO 24V4m and Power Loss vs Load CurrentOUTPUT CURRENT (A) (%)POWER LOSS (mW) = 12 VVOUT = 24 VBurst Mode OPERATIONFIGURE 8 CIRCUITBURSTEFFICIENCYBURSTLOSSLTC378623 786fcFor more information MAXIMUM RATINGSVBIAS .. to 40 VBOOST .. to 71 VSW .. to 65 VRUN .. to 8V Maximum Current Sourced into Pin from Source >8V ..100 APGOOD, PLLIN/MODE .. to 6 VINTVCC, ( Boost SW) .. to 6V(Notes 1, 3)ORDER INFORMATIONLEAD FREE FINISHTAPE AND REELPART MARKING*PACKAGE DESCRIPTIONTEMPERATURE RANGELTC3786 EMSE#PBFLTC3786 EMSE#TRPBF378616-Lead Plastic MSOP 40 C to 125 CLTC3786 IMSE#PBFLTC3786 IMSE#TRPBF378616-Lead Plastic MSOP 40 C to 125 CLTC3786 HMSE#PBFLTC3786 HMSE#TRPBF378616-Lead Plastic MSOP 40 C to 150 CLTC3786 EUD#PBFLTC3786 EUD#TRPBFLFXW16-Lead (3mm 3mm) Plastic QFN 40 C to 125 CLTC3786 IUD#PBFLTC3786 IUD#TRPBFLFXW16-Lead (3mm 3mm) Plastic QFN 40 C to 125 CLTC3786 HUD#PBFLTC3786 HUD#TRPBFLFXW16-Lead (3mm 3mm) Plastic QFN 40 C to 150 CConsult LTC Marketing for parts specified with wider operating temperature ranges.

4 *The temperature grade is identified by a label on the shipping more information on lead free part marking, go to: For more information on tape and reel specifications, go to: Some packages are available in 500 unit reels through designated sales channels with #TRMPBF +SENSE ITHSSPLLIN/MODEFREQRUN161514131211109 PGOODSWTGBOOSTVBIASINTVCCBGGNDTOP VIEW17 GNDMSE PACKAGE16-LEAD PLASTIC MSOP TJMAX = 150 C, JA = 40 C/W, JC = 10 C/W EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB161514135678 TOP VIEW17 GNDUD PACKAGE16-LEAD (3mm 3mm) PLASTIC QFN91011124321 SWPGOODVFBSENSE+BGGNDRUNFREQTGBOOSTVBIAS INTVCCSENSE ITHSSPLLIN/MODE TJMAX = 150 C, JA = 68 C/W, JC = C/W EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCBPIN CONFIGURATIONSENSE+, SENSE.

5 To 40 VSENSE+ SENSE .. to SS, ITH, FREQ, to INTVCCO perating Junction Temperature Range (Notes 2, 3)LTC3786E, LTC3786I .. 40 C to 125 CLTC3786H .. 40 C to 150 CStorage Temperature Range .. 65 C to 150 CLead Temperature (Soldering, 10 sec)MSE Package Only ..300 #orderinfoLTC378633786fcFor more information CHARACTERISTICSThe l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25 C. VBIAS = 12V, unless otherwise noted (Note 2).SYMBOLPARAMETERCONDITIONSMINTYPMAXUNI TSMain Control LoopVBIASChip Bias Voltage Operating Feedback VoltageITH = (Note 4) Current(Note 4) 5 50nAVREFLNREGR eference Line Voltage RegulationVBIAS = 6V to Voltage Load Regulation(Note 4) Measured in Servo Loop; ITH Voltage = to Measured in Servo Loop; ITH Voltage = to 2V l l % %gmError Amplifier TransconductanceITH = DC Supply Current Pulse-Skipping or Forced Continuous Mode Sleep Mode Shutdown(Note 5) RUN = 5V; VFB = (No Load) RUN = 5V.

6 VFB = (No Load) RUN = 0V 55 8 80 20 mA A AUVLOINTVCC Undervoltage Lockout ThresholdsVINTVCC Ramping Up VINTVCC Ramping Downl l V VVRUNRUN Pin On ThresholdVRUN Pin Hysteresis100mVIRUNHYSRUN Pin Hysteresis CurrentVRUN > AIRUNRUN Pin CurrentVRUN < AISSSoft-Start Charge CurrentVSS = 0V71013 AVSENSE(MAX)Maximum Current Sense ThresholdVFB = l687582mVVSENSE(CM)SENSE Pins Common Mode Range ( Boost Converter Input Supply Voltage VIN) +SENSE+ Pin CurrentVFB = AISENSE SENSE Pin CurrentVFB = 1 Atr(TG)Top Gate Rise TimeCLOAD = 3300pF (Note 6)20nstf(TG)Top Gate Fall TimeCLOAD = 3300pF (Note 6)20nstr(BG)Bottom Gate Rise TimeCLOAD = 3300pF (Note 6)20nstf(BG)Bottom Gate Fall TimeCLOAD = 3300pF (Note 6)20nsRUP(TG)Top Gate Pull-Up RDN(TG)Top Gate Pull-Down RUP(BG)Bottom Gate Pull-Up RDN(BG)Bottom Gate Pull-Down tD(TG/BG)Top Gate Off to Bottom Gate On Switch-On Delay TimeCLOAD = 3300pF (Each Driver)80nstD(BG/TG)Bottom Gate Off to Top Gate On Switch-On Delay TimeCLOAD = 3300pF (Each Driver)80nsDFMAXBGM aximum BG Duty Factor96%tON(MIN)Minimum BG On-Time(Note 7)110nsLTC378643786fcFor more information CHARACTERISTICSNote 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device.

7 Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and 2: The LTC3786 is tested under pulsed load conditions such that TJ TA. The LTC3786E is guaranteed to meet specifications from 0 C to 85 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 LTC3786I is guaranteed over the 40 C to 125 C operating junction temperature range. The LTC3786H is guaranteed over the 40 C to 150 C operating temperature range. High temperatures degrade operating lifetimes; operating lifetime is derated for junction temperatures greater than 125 C.

8 Note that the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal impedance and other environmental factors. The junction temperature (TJ in C) is calculated from the ambient temperature (TA in C) and power dissipation (PD in Watts) according to the formula: TJ = TA + (PD JA) The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25 C. VBIAS = 12V, unless otherwise noted (Note 2).SYMBOLPARAMETERCONDITIONSMINTYPMAXUNI TSINTVCC Linear RegulatorVINTVCC(VIN)

9 Internal VCC Voltage6V < VBIAS < INTINTVCC Load RegulationICC = 0mA to and Phase-Locked LoopfPROGP rogrammable FrequencyRFREQ = 25k RFREQ = 60k RFREQ = 100k 335105 400 760 465kHz kHz kHzfLOWL owest Fixed FrequencyVFREQ = 0V320350380kHzfHIGHH ighest Fixed FrequencyVFREQ = INTVCC485535585kHzfSYNCS ynchronizable FrequencyPLLIN/MODE = External Clockl75850kHzPGOOD OutputVPGLPGOOD Voltage LowIPGOOD = Leakage CurrentVPGOOD = 5V 1 AVPGPGOOD Trip LevelVFB with Respect to Set Regulated Voltage VFB Ramping Negative Hysteresis VFB Ramping Positive Hysteresis 12 8 10 10 8 12 % % % %tPGOOD(DELAY)PGOOD DelayPGOOD Going High to Low25 sBOOST Charge PumpIBOOSTBOOST Charge Pump Available Output CurrentVSW = 12V; VBOOST VSW = ; FREQ = 0V, Forced Continuous or Pulse-Skipping Mode85 Awhere JA = 68 C for the QFN package and JA = 40 C for the MSOP 3: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions.

10 The maximum rated junction temperature will be exceeded when this protection is active. Continuous operation above the specified absolute maximum operating junction temperature may impair device reliability or permanently damage the 4: The LTC3786 is tested in a feedback loop that servos VFB to the output of the error amplifier while maintaining ITH at the midpoint of the current limit 5: Dynamic supply current is higher due to the gate charge being delivered at the switching 6: Rise and fall times are measured using 10% and 90% levels. Delay times are measured using 50% 7: see Minimum On-Time Considerations in the Applications Information section.