LTC3736 TM Dual 2-Phase, No R , SENSE Synchronous Controller with Output Tracking FEATURES DESCRIPTIO No Current Sense Resistors Required The LTC 3736 is a 2-phase dual synchronous step-down Out-of-Phase Controllers Reduce Required switching regulator controller with tracking that drives Input Capacitance external complementary power MOSFETs using few exter- Tracking Function nal components. The constant frequency current mode Wide V Range: 2.75V to 9.8V architecture with MOSFET V sensing eliminates the IN DS Constant Frequency Current Mode Operation need for sense resistors and improves efficiency. Power 0.6V 1.5% Voltage Reference loss and noise due to the ESR of the input capacitance are Low Dropout Operation: 100% Duty Cycle minimized by operating the two controllers out of phase. True PLL for Frequency Locking or Adjustment Burst Mode operation provides high efficiency at light loads. Selectable Burst Mode /Forced Continuous Operation 100% duty cycle capability provides low dropout operation, Auxiliary Winding Regulation extending operating time in battery-powered systems. Internal Soft-Start Circuitry The switching frequency can be programmed up to 750kHz, Power Good Output Voltage Monitor allowing the use of small surface mount inductors and ca- Output Overvoltage Protection pacitors. For noise sensitive applications, the LTC3736 Micropower Shutdown: I = 9A Q switching frequency can be externally synchronized from Tiny Low Profile (4mm 4mm) QFN and Narrow 250kHz to 850kHz. Burst Mode operation is inhibited dur- SSOP Packages ing synchronization or when the SYNC/FCB pin is pulled low U in order to reduce noise and RF interference. Automatic soft- APPLICATIO S start is internally controlled. One or Two Lithium-Ion Powered Devices The LTC3736 is available in the tiny thermally enhanced Notebook and Palmtop Computers, PDAs (4mm 4mm) QFN package or 24-lead SSOP narrow Portable Instruments package. Distributed DC Power Systems , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. No R is a trademark of SENSE Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 5929620, 6144194, 6580258, 6304066, 6611131, 6498466. TYPICAL APPLICATIO High Efficiency, 2-Phase, Dual Synchronous DC/DC Step-Down Converter Efficiency vs Load Current V 100 IN 2.75V TO 9.8V 95 10F V IN V = 3.3V IN 2 + + 90 SENSE1 SENSE2 85 V = 4.2V IN TG1 TG2 80 2.2H 2.2H SW1 SW2 V = 5V IN 75 LTC3736 BG1 BG2 70 PGND PGND 65 187k 118k V V OUT1 OUT2 V V 60 FB1 FB2 2.5V 1.8V 55 FIGURE 16 CIRCUIT I I TH1 TH2 220pF V = 2.5V 220pF SGND OUT 47F 47F 50 1 10 100 1000 10000 59k 15k 15k 59k LOAD CURRENT (mA) 3736 TA01b 3736 TA01a 3736fa 1 EFFICIENCY (%) U ULTC3736 ABSOLUTE AXI U RATI GS (Note 1) Input Supply Voltage (V ) ........................ 0.3V to 10V TG1, TG2, BG1, BG2 Peak Output Current (<10s) ..... 1A IN PLLLPF, RUN/SS, SYNC/FCB, Operating Temperature Range (Note 2) ... 40C to 85C + + TRACK, SENSE1 , SENSE2 , Storage Temperature Range .................. 65C to 125C IPRG1, IPRG2 Voltages ................. 0.3V to (V + 0.3V) Junction Temperature (Note 3) ............................ 125C IN V , V , I , I Voltages .................. 0.3V to 2.4V Lead Temperature (Soldering, 10 sec) FB1 FB2 TH1 TH2 SW1, SW2 Voltages ............ 2V to V + 1V or 10V Max (LTC3736EGN) ..................................................... 300C IN PGOOD ..................................................... 0.3V to 10V UUW PACKAGE/ORDER I FOR ATIO TOP VIEW ORDER PART ORDER PART TOP VIEW NUMBER NUMBER + SW1 1 24 SENSE1 IPRG1 2 23 PGND LTC3736EUF LTC3736EGN 24 23 22 21 20 19 V 3 22 BG1 FB1 I 1 18 SYNC/FCB TH1 I 4 21 SYNC/FCB TH1 IPRG2 2 17 TG1 IPRG2 5 20 TG1 PLLLPF 3 16 PGND 25 PLLLPF 6 19 PGND SGND 4 15 TG2 SGND 7 18 TG2 V 5 14 RUN/SS IN V 8 17 RUN/SS IN TRACK 6 13 BG2 UF PART MARKING TRACK 9 16 BG2 7 8 9 10 11 12 V 10 15 PGND FB2 3736 + I 11 14 SENSE2 TH2 PGOOD 12 13 SW2 UF PACKAGE 24-LEAD (4mm 4mm) PLASTIC QFN GN PACKAGE 24-LEAD PLASTIC SSOP T = 125C, = 37C/W JMAX JA EXPOSED PAD (PIN 25) IS PGND T = 125C, = 130C/ W JMAX JA MUST BE SOLDERED TO PCB Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes specifications that apply over the full operating temperature range, otherwise specifications are at T = 25C. V = 4.2V unless otherwise specified. A IN PARAMETER CONDITIONS MIN TYP MAX UNITS Main Control Loops Input DC Supply Current (Note 4) Sleep Mode 300 425 A Shutdown RUN/SS = 0V 9 20 A UVLO V = UVLO Threshold 200mV 3 10 A IN Undervoltage Lockout Threshold V Falling 1.95 2.25 2.55 V IN V Rising 2.15 2.45 2.75 V IN Shutdown Threshold at RUN/SS 0.45 0.65 0.85 V Start-Up Current Source RUN/SS = 0V 0.4 0.7 1 A Regulated Feedback Voltage 0C to 85C (Note 5) 0.591 0.6 0.609 V 40C to 85C 0.588 0.6 0.612 V Output Voltage Line Regulation 2.75V < V < 9.8V (Note 5) 0.05 0.2 mV/V IN 3736fa 2 V V FB2 FB1 I IPRG1 TH2 PGOOD SW1 + SW2 SENSE1 + SENSE2 PGND PGND BG1 U WWW