POWER LOSS (W) LTC3856 2-Phase Synchronous Step-Down DC/DC Controller with Diffamp FeaT DescripT n PolyPhase Controller Reduces Input and Output The LTC 3856 is a single output, dual channel PolyPhase Capacitance and Power Supply Induced Noise synchronous step-down DC/DC controller that drives all n Wide V Range: 4.5V to 38V Operation N-channel power MOSFET stages. This device includes a IN n 0.75%, 0.6V Reference Voltage Accuracy high speed differential amplifier for remote output volt - n High Efficiency: Up to 95% age sense. Power loss and supply noise are minimized by n Programmable Burst Mode Operation or operating the two controller output stages out-of-phase Stage Shedding for Highest Light Load Efficiency and up to 12-phase operation can be achieved. n Active Voltage Positioning (AVP) The LTC3856 monitors the output current by sensing n R or DCR Current Sensing SENSE the voltage drop across the output inductor (DCR) or by n Programmable DCR Temperature Compensation using a sense resistor. DCR temperature compensation n Phase-Lockable Fixed Frequency: 250kHz to 770kHz maintains an accurate current sense threshold over a n True Remote Sense Differential Amplifier broad temperature range. A constant-frequency, current n Dual N-Channel MOSFET Synchronous Drive mode architecture allows a phase-lockable frequency of n V Range: 0.6V to 5V without Differential Amplifier OUT up to 770kHz. n V Range: 0.6V to 3.3V with Differential Amplifier OUT n A wide 4.5V to 38V input supply range encompasses Adjustable Soft-Start or V Tracking OUT n most intermediate bus voltages and battery chemistries. Stackable for Up to 12-Phase Operation n Burst Mode operation, continuous or Stage Shedding 32-Pin (5mm 5mm) QFN and 38-Pin TSSOP Packages modes are supported. A TK/SS pin shared by both chan- Ta nels ramps the output voltage during start-up. n Telecom and Datacom Systems L, LT, LTC, LTM, Linear Technology, the Linear logo, PolyPhase, Burst Mode and OPTI-LOOP are registered trademarks and Stage Shedding is a trademark of Linear Technology Corporation. n Industrial and Medical Instruments All other trademarks are the property of their respective owners. Protected by U.S. Patents, n including 5481178, 5705919, 5929620, 6100678, 6144194, 6177787, 6304066, 6498466, DC Power Distribution Systems 6580258, 6611131, 6674274. n Computer Systems Typical Ta Efficiency and Power Loss High Efficiency 1.5V/50A Step-Down Converter vs Output Current V 100 100 IN 4.5V TO V = 12V IN 30.1k 10F 20V 90 4 V = 1.5V DIFFOUT V TG1 OUT IN 0.33H Burst Mode V BOOST1 FB 0.1F 80 OPERATION ILIM SW1 10 20k LTC3856 70 RUN BG1 PGOOD PLLIN 60 + CLKOUT SENSE1 50 1 PHASMD SENSE1 MODE TG2 40 0.33H V OUT ITEMP BOOST2 0.1F 1.5V 30 FREQ SW2 50A 0 BG2 20 122k EXTV INTV CC CC + 10 100F DIFFN SENSE2 4.7F 8 DIFFP SENSE2 0 1 0.1 1 10 100 I TK/SS GND AVP ISET TH 2200pF LOAD CURRENT (A) 0.1F 3856 TA01b 1.5k 3856 TA01a 3856fa 1 For more information www.linear.com/LTC3856 EFFICIENCY (%) S S S S S S S S S S S S ion pplica ions pplica ion uresLTC3856 Ta e MaxiMMu Tar (Note 1) Input Supply Voltage (V ) ......................... 40V to 0.3V I , V Voltages ................................... INTV to 0.3V IN TH FB CC Topside Driver Voltages (BOOSTn) ............ 46V to 0.3V INTV Peak Output Current ................................100mA CC Switch Voltage (SWn) ................................... 40V to 5V Operating Junction Temperature Range INTV , RUN, PGOOD, EXTV , (Notes 2, 3) ............................................ 40C to 125C CC CC (BOOSTn SWn) ......................................... 6V to 0.3V Storage Temperature Range ................... 65C to 125C SENSEn Voltages ...................................... 5.5V to 0.3V Reflow Peak Body Temperature (UH Package) ...... 260C MODE, PLLIN, ILIM, TK/SS, AVP, Lead Temperature (Soldering, 10 sec.) FREQ, ISET Voltages ............................. INTV to 0.3V FE Package ............................................................ 300C CC DIFFP, DIFFN, DIFFOUT, PHASMD, ITEMP Voltages ..................................... INTV to 0.3V CC in p Fc T TOP VIEW 1 PLLIN FREQ 38 RUN 2 CLKOUT 37 TOP VIEW + SENSE1 3 SW1 36 SENSE1 4 TG1 35 NC 5 NC 34 TK/SS 6 BOOST1 32 31 30 29 28 27 26 25 33 TK/SS 1 24 BOOST1 V 7 PGND1 32 FB V 2 23 BG1 I 8 BG1 FB 31 TH I 3 22 V TH IN SGND 9 30 V IN 39 AVP 4 21 INTV CC 33 AVP 10 29 INTV CC SGND SGND/PGND ITEMP 5 20 EXTV CC ITEMP 11 28 EXTV CC PHASMD 6 19 BG2 PHASMD 12 27 BG2 + SENSE2 7 18 BOOST2 + SENSE2 13 26 PGND2 SENSE2 8 17 TG2 SENSE2 14 25 NC 9 10 11 12 13 14 15 16 DIFFP 15 24 BOOST2 DIFFN 16 23 TG2 DIFFOUT 17 22 SW2 ISET 18 21 PGOOD UH PACKAGE 32-LEAD (5mm 5mm) PLASTIC QFN ILIM 19 20 MODE T = 125C, = 34C/W JMAX JA FE PACKAGE EXPOSED PAD (PIN 33) IS SGND/PGND, MUST BE SOLDERED TO PCB 38-LEAD PLASTIC TSSOP T = 125C, = 25C/W JMAX JA EXPOSED PAD (PIN 39) IS SGND/PGND, MUST BE SOLDERED TO PCB 3856fa 2 For more information www.linear.com/LTC3856 DIFFP SENSE1 + DIFFN SENSE1 DIFFOUT RUN ISET FREQ ILIM PLLIN MODE CLKOUT PGOOD SW1 SW2 TG1 ion igura on ings bsolu