LTC7818 40V, Low I , 3MHz, Q Triple Output Buck/Buck/Boost Synchronous Controller FEATURES DESCRIPTION n Dual Buck Plus Single Boost Synchronous Controllers The LTC 7818 is a high performance triple output (buck/ n buck/boost) synchronous DC/DC switching regulator con- Low Operating I : Q n troller that drives all N-channel power MOSFET stages. 14A (14V to 3.3V, Channel 1 On) n Its constant-frequency current mode architecture allows Outputs Remain in Regulation Through Cold Crank a phase-lockable switching frequency of up to 3MHz. Down to 1V Input Supply Voltage The LTC7818 operates from a wide 4.5V to 40V input n Wide Bias Input Voltage Range: 4.5V to 40V supply range. When biased from the output of the boost n Buck and Boost Output Voltages Up to 40V converter or another auxiliary supply, the LTC7818 can n Spread Spectrum Operation operate from an input supply as low as 1V after start-up. n R or DCR Current Sensing SENSE n The LTC7818 synchronous boost PassThru capability Programmable Fixed Frequency (100kHz to 3MHz) n minimizes losses in automotive start-stop applications. PassThru/100% Duty Cycle Capable for The very low no-load quiescent current extends operating Synchronous Boost MOSFET run time in battery powered systems. OPTI-LOOP com- n Phase-Lockable Frequency (100kHz to 3MHz) pensation allows the transient response to be optimized n Selectable Continuous, Pulse-Skipping, or Low over a wide range of output capacitance and ESR values. Ripple Burst Mode Operation at Light Loads The LTC7818 features a precision 0.8V reference for the n Boost Channel Current Monitor Output bucks, 1.2V reference for the boost and a power good n Low Shutdown I : 1.5A Q output indicator. n Small 40-Lead 6mm 6mm QFN Package n The LTC7818 additionally features spread spectrum oper- AEC-Q100 Qualified for Automotive Applications ation which significantly reduces the peak radiated and conducted noise on both the input and output supplies, APPLICATIONS making it easier to comply with electromagnetic interfer- n Automotive and Transportation ence (EMI) standards. n Industrial All registered trademarks and trademarks are the property of their respective owners. Protected n Military/Avionics by U.S. Patents including 5481178, 5705919, 5929620, 6144194, 6177787, 6580258. TYPICAL APPLICATION V OUT3 LTC7818 Response to a Cold LTC7818 Response to a Cold Crank REGULATED TO 10V Crank Automotive Waveform WHEN V < 10V IN VBIAS 150F 22F V FB3 Automotive Waveform FOLLOWS V IN TG3 TG1 WHEN V >10V IN BOOST3 BOOST1 0.1F 0.1F 1.4H 0.9H 1.5m V 2m OUT1 3.3V V SW3 IN SW1 12A V BATT 1V TO 38V 22F 330F STARTUP V OUT3 150F BG3 BG1 ABOVE 5V LTC7818 210k SENSE3 SENSE1+ + SENSE3 SENSE1 VOLTAGE V FB1 V RUN1,2,3 OUT3 V OUT3 2V/DIV 68.1k ITH1,2,3 V TRACK/SS1,2,3 OUT2 TG2 INTV CC BOOST2 V VPRG3 0.1F OUT1 1.8H 3m V OUT2 0.1F 4.7F 5V SW2 10A BG2 330F 10F BOOST1,2,3 MODE + SENSE2 357k 0V PLLIN/SPREAD 7818 TA01b SENSE2 TIME (10ms/DIV) FREQ V FB2 EXTV V CC OUT2 GND 68.1k 7818 TA01a Rev. B 1 Document Feedback For more information www.analog.comLTC7818 TABLE OF CONTENTS Features ..................................................... 1 Low Value Resistor Current Sensing ....................... 19 Applications ................................................ 1 Inductor DCR Current Sensing ................................20 Typical Application ........................................ 1 Setting the Operating Frequency.............................21 Description.................................................. 1 Selecting the Light Load Operating Mode ...............22 Absolute Maximum Ratings .............................. 3 Power MOSFET Selection .......................................23 Order Information .......................................... 3 Boost C and C Selection ................................. 24 IN OUT Pin Configuration .......................................... 3 Buck C and C Selection .................................. 24 IN OUT Electrical Characteristics ................................. 4 Setting the Buck Output Voltage .............................25 Typical Performance Characteristics ................... 7 Setting Boost Output Voltage (VPRG3 Pin) ............26 Pin Functions .............................................. 11 RUN Pins and Undervoltage Lockout ......................26 Functional Diagram ...................................... 13 Soft-Start and Tracking (TRACK/SS1, TRACK/SS2, Operation................................................... 14 SS3 Pins) ................................................................26 Main Control Loop .................................................. 14 Single Output Two-Phase Operation .......................27 Power and Bias Supplies (V , EXTV , and INTV Regulators ..................................................28 BIAS CC CC INTV ) .................................................................. 14 Topside MOSFET Driver Supply (C , D ) ................29 CC B B Shutdown and Start-Up (RUN1, RUN2, RUN3 and Minimum On-Time Considerations..........................29 TRACK/SS1, TRACK/SS2, SS3 Pins) ...................... 14 Boost Channel Current Monitor (IMON3) ................29 Light Load Operation: Burst Mode Operation, Pulse- Fault Conditions: Buck Current Limit and Foldback .30 Skipping, or Forced Continuous Mode (MODE Pin) 15 Fault Conditions: Buck Overvoltage Protection Frequency Selection, Spread Spectrum, and Phase- (Crowbar) ................................................................30 Locked Loop (FREQ and PLLIN/SPREAD Pins) ....... 16 Fault Conditions: Overtemperature Protection ........30 Boost Controller Operation When V > V Phase-Locked Loop and Frequency Synchronization 30 IN OUT ............. 16 Boost Controller at Low Input Voltage .................... 17 Efficiency Considerations .......................................31 Buck Controller Output Overvoltage Protection ...... 17 Checking Transient Response .................................32 Buck Foldback Current ............................................ 17 Buck Design Example .............................................32 Channel 1 Power Good (PGOOD1) .......................... 17 PC Board Layout Checklist .....................................34 Boost Overvoltage Indicator (OV3) ......................... 17 PC Board Layout Debugging ...................................35 Applications Information ................................ 18 Typical Applications ...................................... 37 Inductor Value Calculation ...................................... 18 Package Description ..................................... 42 Inductor Core Selection .......................................... 18 Revision History .......................................... 43 Current Sense Selection ......................................... 19 Typical Application ....................................... 44 Related Parts .............................................. 44 Rev. B 2 For more information www.analog.com