LTC7812 Low I , 38V Synchronous Q Boost+Buck Controller FEATURES DESCRIPTION n Synchronous Boost and Buck Controllers The LTC 7812 is a high performance synchronous n When Cascaded, Allows V Above, Below or Equal Boost+Buck DC/DC switching regulator controller that IN to Regulated V drives all N-channel power MOSFET stages. It contains OUT n Output Remains in Regulation Through Input Dips independent step-up (boost) and step-down (buck) control- (e.g., Cold Crank) Down to 2.5V lers that can regulate two separate outputs or be cascaded n to regulate an output voltage from an input voltage that Wide Bias Input Voltage Range: 4.5V to 38V n can be above, below or equal to the output voltage. The Low Input and Output Ripple n LTC7812 operates from a wide 4.5V to 38V input supply Low EMI n range. When biased from the output of the boost regulator, Fast Output Transient Response n the LTC7812 can operate from an input supply as low as High Light Load Efficiency n 2.5V after start-up. The 33A no-load quiescent current Low Operating I : 33A (Both Channels On) Q n extends operating run time in battery-powered systems. Low Operating I : 28A (Buck Channel On) Q n R or Lossless DCR Current Sensing SENSE Unlike conventional buck-boost regulators, the LTC7812s n Buck Output Voltage Range: 0.8V V 24V OUT cascaded Boost+Buck solution has continuous, non- n Boost Output Voltage Up to 60V pulsating, input and output currents, substantially reducing n Phase-Lockable Frequency (75kHz to 850kHz) voltage ripple and EMI. The LTC7812 has independent n Small 32-Pin 5mm 5mm QFN Package feedback and compensation points for the boost and buck regulation loops, enabling a fast output transient response APPLICATIONS that can be easily optimized externally. n Automotive and Industrial Power Systems L, LT, LTC, LTM, Burst Mode, OPTI-LOOP and Module are registered trademarks and n No R is a trademark of Analog Devices, Inc. All other trademarks are the property of their High Power Battery Operated Systems SENSE respective owners. TYPICAL APPLICATION Wide Input Range to 12V/8A Low I , Cascaded Boost+Buck Regulator Q V IN 5V TO 38V 2m 1H V , 14V** 4.7H 3m V MID OUT DOWN TO 12V + 33F 6.8F 6.8F + 33F 22F + 47F 2.5V AFTER 8A* 499k 499k START-UP 46.4k 35.7k 4.7F 0.1F 0.1F + + SENSE2 SENSE2 BG2 SW2 BOOST2 TG2 INTV PGND V V TG1 BOOST1 SW1 BG1 SENSE1 SENSE1 V CC FB2 BIAS FB1 EXTV LTC7812 CC I I RUN1 RUN2 TH1 TH2 TRACK/SS1 SS2 FREQ PLLIN/MODE SGND 0.1F 15k 1.86k 0.01F 100pF 820pF * WHEN V < 8V, MAXIMUM LOAD CURRENT AVAILABLE IS REDUCED IN 4.7nF 6.8nF ** V = 14V WHEN V < 14V MID IN V FOLLOWS V WHEN V > 14V 7812 TA01a MID IN IN 7812fc 1 For more information www.linear.com/LTC7812LTC7812 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) Bias Input Supply Voltage (V ) .............. 0.3V to 40V BIAS TOP VIEW Buck Top Side Driver Voltage (BOOST1) .... 0.3V to 46V Boost Top Side Driver Voltage (BOOST2) .... 0.3V to 76V Buck Switch Voltage (SW1) ......................... 5V to 40V 32 31 30 29 28 27 26 25 Boost Switch Voltage (SW2) ........................ 5V to 70V SW1 1 24 INTV CC INTV , (BOOST1SW1), CC TG1 2 23 NC (BOOST2SW2) ...................................... 0.3V to 6V PGOOD1 3 22 OV2 RUN1, RUN2 ............................................... 0.3V to 8V TRACK/SS1 4 21 SGND 33 Maximum Current Sourced Into Pin I SGND 5 PGND 20 TH1 from Source >8V ..............................................100A V 6 19 RUN2 FB1 + BG1, BG2, TG1, TG2 ........................................... (Note 8) SENSE1 7 18 SGND + SENSE1 8 17 RUN1 SENSE1 , SENSE1 Voltages ...................... 0.3V to 28V + 9 10 11 12 13 14 15 16 SENSE2 , SENSE2 Voltages ..................... 0.3V to 40V FREQ Voltage ........................................0.3V to INTV CC EXTV ...................................................... 0.3V to 14V CC I , I , V , V , Voltages .................... 0.3V to 6V UH PACKAGE TH1 TH2 FB1 FB2 32-LEAD (5mm 5mm) PLASTIC QFN PLLIN/MODE, PGOOD1, OV2 Voltages ........ 0.3V to 6V T = 150C, q = 44C/W JMAX JA TRACK/SS1, SS2 Voltages .......................... 0.3V to 6V EXPOSED PAD (PIN 33) IS PGND, MUST BE SOLDERED TO PCB Operating Junction Temperature Range (Notes 2, 3) LTC7812E, LTC7812I .......................... 40C to 125C LTC7812H .......................................... 40C to 150C Storage Temperature Range .............. 65C to 150C ORDER INFORMATION