POWER LOSS (mW) LTC3836 Dual 2-Phase, TM No R Low V SENSE IN Synchronous Controller FEATURES DESCRIPTION n No Current Sense Resistors Required The LTC 3836 is a 2-phase dual output synchronous n Out-of-Phase Controllers Reduce Required Input step-down switching regulator controller with tracking Capacitance that drives external N-channel power MOSFETs using few n All N-Channel Synchronous Drive external components. The constant-frequency current n V Range: 2.75V to 4.5V mode architecture with MOSFET V sensing eliminates IN DS n Constant-Frequency Current Mode Operation the need for sense resistors and improves ef ciency. n 0.6V 1.5% Voltage Reference The power loss and noise due to the ESR of the input n Low Dropout Operation: 97% Duty Cycle capacitance are minimized by operating the two control- n True PLL for Frequency Locking or Adjustment lers out-of-phase. Pulse-skipping operation provides high n Selectable Pulse-Skipping/Continuous Operation ef ciency at light loads. The 97% duty cycle capability n Tracking Function provides low dropout operation, extending operating time n Internal Soft-Start Circuitry in battery-powered systems. n Power Good Output Voltage Monitor The operating frequency is selectable from 300kHz to n Output Overvoltage Protection 750kHz, allowing the use of small surface mount induc- n Micropower Shutdown: I = 6.5A Q tors and capacitors. For noise sensitive applications, the n Tiny Low Pro le (4mm 5mm) QFN and Narrow LTC3836 operating frequency can be externally synchro- SSOP Packages nized from 250kHz to 850kHz. The LTC3836 features an internal 1ms soft-start that can APPLICATIONS be extended with an external capacitor. A tracking input al- n General Purpose 3.3V to 1.X Supplies lows the second output to track the rst during start-up. n Single Lithium-Ion Powered Devices The LTC3836 is available in the tiny thermally enhanced n Distributed DC Power Systems (4mm 5mm) QFN and 28-lead narrow SSOP packages. L, LT, LTC, LTM, Linear Technology, Burst Mode, OPTI-LOOP and the Linear logo are registered trademarks and No R is a trademark of Linear Technology Corporation. All other SENSE trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 5929620, 6144194, 6304066, 6498466, 6580258, 6611131. TYPICAL APPLICATION High Ef ciency, 2-Phase, Dual Synchronous DC/DC Step-Down Converter Ef ciency/Power Loss vs Load Current 100 10000 V IN 3.3V-1.8V 3.3V 90 EFFICIENCY 22F V IN 3 BOOST1 BOOST2 80 3.3V-1.2V + + SENSE1 SENSE2 1000 EFFICIENCY 70 TG1 TG2 60 0.47H 0.47H SW1 SW2 50 100 LTC3836 3.3V-1.2V BG1 BG2 40 POWER LOSS PGND 30 3.3V-1.8V 118k 59k 10 V V OUT1 OUT2 POWER LOSS V V 20 FB1 FB2 1.8V AT 1.2V AT I I TH1 TH2 15A 15A 10 820pF 820pF SGND CIRCUIT OF FIGURE 15 59k 100F 100F 0 1 59k 15k 15k 2 2 10 100 1000 10000 100000 LOAD CURRENT (mA) 3836 TA01b 3836 TA01 3836fb 1 EFFICIENCY (%)LTC3836 ABSOLUTE MAXIMUM RATINGS (Note 1) BOOST1, BOOST2 Voltages ....................... 0.3V to 10V SW1, SW2 Voltages ............................... 2V to V + 1V IN Input Supply Voltage (V ) ........................ 0.3V to 4.5V PGOOD ....................................................... 0.3V to 10V IN PLLLPF, RUN/SS, SYNC/FCB, Operating Temperature Range (Note 2).... 40C to 85C + + SENSE1 , SENSE2 , Storage Temperature Range ................... 65C to 125C IPRG1, IPRG2 Voltages ..................0.3V to (V + 0.3V) IN Junction Temperature (Note 3) ............................. 125C V , V , I , I , FB1 FB2 TH1 TH2 TRACK/SS2 Voltages ................................ 0.3V to 2.4V PIN CONFIGURATION TOP VIEW TOP VIEW + SW1 1 28 SENSE1 N/C 2 27 BOOST1 IPRG1 3 26 PGND 28 27 26 25 24 23 VFB1 1 22 BG1 V 4 25 BG1 FB1 ITH1 2 21 SYNC/FCB I 5 24 SYNC/FCB TH1 IPRG2 3 20 TG1 IPRG2 6 23 TG1 PLLLPF 4 19 PGND 29 PLLLPF 7 22 PGND SGND 5 18 TG2 SGND 8 21 TG2 V 6 17 RUN/SS IN V 9 20 RUN/SS IN TRACK/SS2 7 16 N/C TRACK/SS2 10 19 BG2 VFB2 8 15 BG2 V 11 18 N/C FB2 9 10 11 12 13 14 I 12 17 PGND TH2 PGOOD 13 16 BOOST2 + SENSE2 SW2 14 15 UFD PACKAGE 28-LEAD (4mm 5mm) PLASTIC QFN GN PACKAGE 28-LEAD PLASTIC SSOP T = 125C, = 43C/W JMAX JA EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB T = 125C, = 90C/W JMAX JA ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3836EGN PBF LTC3836EGN TRPBF LTC3836EGN 28-Lead Plastic SSOP 40C to 85C LTC3836EUFD PBF LTC3836EUFD TRPBF 3836 28-Lead (4mm 5mm) Plastic QFN 40C to 85C Consult LTC Marketing for parts speci ed with wider operating temperature ranges. Consult LTC Marketing for information on non-standard lead based nish parts. For more information on lead free part marking, go to: