LTC3859 Low I , Triple Output, Q Buck/Buck/Boost Synchronous Controller FEATURES DESCRIPTION n Dual Buck Plus Single Boost Synchronous Controllers The LTC 3859 is a high performance triple output (buck/ n Outputs Remain in Regulation Through Cold Crank buck/boost) synchronous DC/DC switching regulator Down to 2.5V controller that drives all N-channel power MOSFET stages. n Constant frequency current mode architecture allows a Low Operating I : 55A (One Channel On) Q n phase-lockable switching frequency of up to 850kHz. The Wide Bias Input Voltage Range: 4.5V to 38V n LTC3859 operates from a wide 4.5V to 38V input supply Buck Output Voltage Range: 0.8V V 24V OUT n range. When biased from the output of the boost converter Boost Output Voltage Up to 60V n or another auxiliary supply, the LTC3859 can operate from R or DCR Current Sensing SENSE an input supply as low as 2.5V after start-up. n 100% Duty Cycle for Boost Synchronous MOSFET n Phase-Lockable Frequency (75kHz to 850kHz) The 55A no-load quiescent current extends operating run- n Programmable Fixed Frequency (50kHz to 900kHz) time in battery powered systems. OPTI-LOOP compensation n Selectable Continuous, Pulse-Skipping or Low Ripple allows the transient response to be optimized over a wide Burst Mode Operation at Light Loads range of output capacitance and ESR values. The LTC3859 n Very Low Buck Dropout Operation: 99% Duty Cycle features a precision 0.8V reference for the bucks, 1.2V n Adjustable Output Voltage Soft-Start or Tracking reference for the boost and a power good output indicator. n Low Shutdown I : 14A Q Independent TRACK/SS pins for each controller ramp the out- n Small 38-Pin 5mm 7mm QFN and TSSOP Packages put voltages during start-up. Current foldback limits MOSFET heat dissipation during short-circuit conditions. The PLLIN/ APPLICATIONS MODE pin selects among Burst Mode operation, pulse-skipping mode, or continuous inductor current mode at light loads. n Automotive Always-On and Start-Stop Systems n All registered trademarks and trademarks are the property of their respective owners. Protected Battery Operated Digital Devices by U.S. Patents including 5481178, 5705919, 5929620, 6144194, 6177787, 6580258. n Distributed DC Power Systems TYPICAL APPLICATION V OUT3 REGULATED AT 10V WHEN V < 10V IN 220F 1F FOLLOWS V WHEN V > 10V IN IN 499k V BIAS Efficiency vs Input Voltage V FB3 TG1 68.1k 100 4.9H V 6m OUT1 V = 8.5V 95 OUT2 5V TG3 SW1 1.2H V 2m IN 5A 90 V = 5V OUT1 2.5V TO 38V SW3 BG1 LTC3859 (START-UP ABOVE 5V) 85 220F BG3 + 80 SENSE1 SENSE1 75 SENSE3 + V SENSE3 FB1 70 357k INTV CC 68.1k 220F 65 RUN1, 2, 3 4.7F 60 BOOST1, 2, 3 EXTV CC 0.1F FIGURE 12 CIRCUIT 55 SW1, 2, 3 TG2 I = 2A LOAD 6.5H V 8m OUT2 50 8.5V I SW2 TH1, 2, 3 0 5 10 15 20 25 30 35 40 3A BG2 INPUT VOLTAGE (V) 3859 TA01b SENSE2+ TRACK/SS1, 2 SENSE2 0.1F SS3 V FB2 649k PGND SGND 68.1k 68F 3859 TA01 Rev. C 1 Document Feedback For more information www.analog.com EFFICIENCY (%)LTC3859 ABSOLUTE MAXIMUM RATINGS (Notes 1, 3) + + Bias Input Supply Voltage (V ) .............. 0.3V to 40V SENSE1 , SENSE2 , SENSE1 BIAS Buck Top Side Driver Voltages SENSE2 Voltages ..................................... 0.3V to 28V + (BOOST1, BOOST2) ............................. 0.3V to 46V SENSE3 , SENSE3 Voltages ..................... 0.3V to 40V Boost Top Side Driver Voltages FREQ Voltages ......................................0.3V to INTV CC (BOOST3) ............................................ 0.3V to 76V EXTV ...................................................... 0.3V to 14V CC Buck Switch Voltage (SW1, SW2) ................ 5V to 40V I , I , I , V , V , V Voltages .... 0.3V to 6V TH1 TH2 TH3 FB1 FB2 FB3 Boost Switch Voltage (SW3) ........................ 5V to 70V PLLIN/MODE, PGOOD1, OV3 Voltages ........ 0.3V to 6V , (BOOST1SW1), TRACK/SS1, TRACK/SS2, SS3 Voltages ..... 0.3V to 6V INTV CC (BOOST2SW2), (BOOST3SW3), .......... 0.3V to 6V Operating Junction Temperature Range RUN1, RUN2, RUN3 .................................... 0.3V to 8V (Note 2) ............................................. 40C to 125C Maximum Current Sourced Into Pin Storage Temperature Range .................. 65C to 150C from Source >8V ..............................................100A PIN CONFIGURATION TOP VIEW TOP VIEW 1 38 TRACK/SS1 I TH1 2 37 PGOOD1 V FB1 + 3 36 TG1 SENSE1 38 37 36 35 34 33 32 4 35 SW1 SENSE1 FREQ 1 31 SW1 5 34 BOOST1 FREQ PLLIN/MODE 2 30 BOOST1 6 33 BG1 PLLIN/MODE SS3 3 29 BG1 7 32 SW3 SS3 + SENSE3 4 28 SW3 + 8 31 TG3 SENSE3 SENSE3 5 27 TG3 9 30 BOOST3 SENSE3 V 6 26 BOOST3 FB3 39 39 10 29 BG3 V FB3 PGND PGND I 7 25 BG3 TH3 11 28 V I TH3 BIAS SGND 8 24 V BIAS 12 27 EXTV SGND CC RUN1 9 23 EXTV CC 13 26 INTV RUN1 CC RUN2 10 22 INTV CC 14 25 BG2 RUN2 21 RUN3 11 BG2 15 24 BOOST2 RUN3 SENSE2 12 20 BOOST2 16 23 SW2 SENSE2 13 14 15 16 17 18 19 + 17 22 TG2 SENSE2 18 21 OV3 V FB2 19 20 TRACK/SS2 I TH2 UHF PACKAGE FE PACKAGE 38-LEAD (5mm 7mm) PLASTIC QFN 38-LEAD PLASTIC TSSOP T = 125C, q = 34C/W JMAX JA T = 125C, q = 25C/W EXPOSED PAD (PIN 39) IS PGND, MUST BE SOLDERED TO PCB JMAX JA EXPOSED PAD (PIN 39) IS PGND, MUST BE SOLDERED TO PCB Rev. C 2 For more information www.analog.com + SENSE1 SENSE2 + V SENSE1 FB2 I V TH2 FB1 TRACK/SS2 I TH1 OV3 TRACK/SS1 PGOOD1 TG2 SW2 TG1