LTC3855 Dual, Multiphase Synchronous DC/DC Controller with Differential Remote Sense Fae Tseru Dpircse Tnoi n Dual, 180 Phased Controllers Reduce Required The LTC 3855 is a dual PolyPhase current mode synchro- Input Capacitance and Power Supply Induced Noise nous step-down switching regulator controller that drives n High Efficiency: Up to 95% all N-channel power MOSFET stages. It includes a high n R or DCR Current Sensing speed differential remote sense amplifier. The maximum SENSE n Programmable DCR Temperature Compensation current sense voltage is programmable for either 30mV, n 0.75% 0.6V Output Voltage Accuracy 50mV or 75mV, allowing the use of either the inductor DCR n Phase-Lockable Fixed Frequency 250kHz to 770kHz or a discrete sense resistor as the sensing element. n True Remote Sensing Differential Amplifier The LTC3855 features a precision 0.6V reference and can n Dual N-Channel MOSFET Synchronous Drive produce output voltages up to 12.5V. A wide 4.5V to 38V n Wide V Range: 4.5V to 38V IN input supply range encompasses most intermediate bus n V Range: 0.6V to 12.5V without Differential Ampliefi r OUT voltages and battery chemistries. Power loss and supply n V Range: 0.6V to 3.3V with Differential Amplifier OUT noise are minimized by operating the two controller output n Clock Input and Output for Up to 12-Phase Operation stages out of phase. Burst Mode operation, continuous n Adjustable Soft-Start or V Tracking OUT or pulse-skipping modes are supported. n Foldback Output Current Limiting n The LTC3855 can be configured for up to 12-phase op- Output Overvoltage Protection n eration, has DCR temperature compensation, two power 40-Pin (6mm 6mm) QFN and 38-Lead FE Packages good signals and two current limit set pins. The LTC3855 is available in low profile 40-pin 6mm 6mm QFN and a acilpp Tsnoi 38-lead exposed pad FE packages. n Computer Systems L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode and PolyPhase are registered n trademarks of Linear Technology Corporation. All other trademarks are the property of their Telecom Systems respective owners. Protected by U.S. Patents including 5481178, 5705919, 5929620, 6100678, n Industrial and Medical Instruments 6144194, 6177787, 6304066, 6580258. n DC Power Distribution Systems T lacipy a acilpp Tnoi High Efficiency Dual 1.8V/1.2V Step-Down Converter V IN Load Step 4.5V TO + 20V 22F (Forced Continuous Mode) 4.7F 1F V INTV IN CC TG1 TG2 I LOAD 0.1F 0.1F 5A/DIV BOOST1 BOOST2 0.4H 0.56H 300mA TO 5A SW1 SW2 BG1 BG2 I L PGND1 PGND2 5A/DIV LTC3855 FREQ + + SENSE1 SENSE2 SENSE2 SENSE1 V OUT 20k V OUT1 V 100mV/DIV DIFFOUT OUT2 1.8V AC-COUPLED V 1.2V FB1 V FB2 15A 40.2k 15A I I TH1 TH2 470pF 470pF TK/SS1 DIFFP SGND DIFFN TK/SS2 + + 330F 330F 20k 7.5k 3855 TA01a 100k 15k 50s/DIV 2 0.1F 0.1F 2 20k V = 12V IN V = 1.8V OUT 3855 TA01 3855f LTC3855 a ulosb T e Mixa Mu M r a Tsgni (Note 1) Input Supply Voltage (V ) .........................0.3V to 40V DIFFP, DIFFN ..........................................0.3V to INTV IN CC Top Side Driver Voltages ITEMP1, ITEMP2 Voltages ....................0.3V to INTV CC BOOST1, BOOST2 ..................................0.3V to 46V I , I , V , V Voltages ..............0.3V to INTV TH1 TH2 FB1 FB2 CC Switch Voltage (SW1, SW2) .........................5V to 40V INTV Peak Output Current (Note 8) ..................100mA CC INTV , RUN1, RUN2, PGOOD(s), EXTV , Operating Junction Temperature Range (Notes 2, 3) CC CC (BOOST1-SW1), (BOOST2-SW2) .............0.3V to 6V LTC3855 .............................................40C to 125C + + SENSE1 , SENSE2 , SENSE1 , Storage Temperature Range ...................65C to 125C SENSE2 Voltages .................................0.3V to 13V Lead Temperature (Soldering, 10 sec) MODE/PLLIN, I , I , TK/SS1, TK/SS2, FREQ, (FE Package) ..................................................... 300C LIM1 LIM2 DIFFOUT, PHASMD Voltages .............0.3V to INTV CC p ni c no Farugi Tnoi TOP VIEW ITEMP2 1 38 FREQ TOP VIEW ITEMP1 2 37 MODE/PLLIN RUN1 3 36 PHASMD + SENSE1 4 35 CLKOUT SENSE1 5 34 SW1 40 39 38 37 36 35 34 33 32 31 TK/SS1 6 33 TG1 TK/SS1 1 30 TG1 I 7 32 BOOST1 TH1 I 2 29 BOOST1 TH1 V 8 31 PGND1 V 3 28 PGND1 FB1 FB1 V 9 30 BG1 SGND 4 27 BG1 FB2 39 I 10 29 V V 5 26 V IN FB2 41 IN TH2 SGND SGND I 6 25 INTV TK/SS2 11 28 INTV TH2 CC CC + TK/SS2 7 24 EXTV 12 SENSE2 27 EXTV CC CC + SENSE2 8 23 BG2 13 SENSE2 26 BG2 SENSE2 9 22 PGND2 14 DIFFP 25 PGND2 DIFFP 10 21 BOOST2 15 DIFFN 24 BOOST2 11 12 13 14 15 16 17 18 19 20 16 DIFFOUT 23 TG2 17 RUN2 22 SW2 18 I 21 PGOOD2 LIM1 UJ PACKAGE 19 I 20 PGOOD1 LIM2 40-LEAD (6mm 6mm) PLASTIC QFNs T = 125C, = 33C/W JMAX JA FE PACKAGE EXPOSED PAD (PIN 41) IS SGND, MUST BE SOLDERED TO PCB 38-LEAD PLASTIC SSOP T = 125C, = 25C/W JMAX JA EXPOSED PAD (PIN 39) IS SGND, MUST BE SOLDERED TO PCB 3855f DIFFN SENSE1 + DIFFOUT SENSE1 RUN2 RUN1 I ITEMP1 LIM1 I ITEMP2 LIM2 PGOOD1 FREQ PGOOD2 MODE/PLLIN NC PHASMD SW2 CLKOUT TG2 SW1