LTC3737 Dual 2-Phase, No R TM SENSE , DC/DC Controller with Output Tracking UFEATURESDESCRIPTIO ■ Sense Resistor Optional The LTC®3737 is a 2-phase dual step-down switching ■ Out-of-Phase Controllers Reduce Required regulator controller that requires few external compo- Input Capacitance nents. The constant frequency current mode architecture ■ Programmable Output Voltage Tracking provides excellent AC and DC load and line regulation. ■ Constant Frequency Current Mode Architecture MOSFET VDS sensing eliminates the need for current ■ Wide VIN Range: 2.75V to 9.8V sense resistors and improves efficiency. Power loss and ■ Wide VOUT Range: 0.6V to VIN noise due to the ESR of the input capacitance are mini- ■ 0.6V ±1.5% Reference mized by operating the two controllers out of phase. ■ Low Dropout Operation: 100% Duty Cycle Burst Mode operation provides high efficiency operation ■ True PLL for Frequency Locking or Adjustment at light loads. 100% duty cycle provides low dropout (Frequency Range 250kHz to 850kHz) operation and extends battery operating time. ■ Selectable Burst Mode® or Pulse Skipping Operation at Light Loads Switching frequency can be programmed up to 750kHz, ■ Internal Soft-Start Circuitry allowing the use of small surface mount inductors and ■ Selectable Maximum Peak Current Sense Threshold capacitors. For noise sensitive applications, the LTC3737 ■ Power Good Output Voltage Monitor can be externally synchronized from 250kHz to 850kHz. ■ Output Overvoltage Protection Other features include a power good output voltage moni- ■ Micropower Shutdown: IQ = 9µA tor, a tracking input and internal soft-start. ■ Tiny 4mm × 4mm QFN and 24-Lead SSOP Packages The LTC3737 is available in the low profile thermally U enhanced (4mm APPLICATIO S × 4mm) QFN package or a 24-lead SSOP narrow package. ■ One or Two Lithium-Ion Powered Devices , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode ■ Notebook and Palmtop Computers, PDAs is a registered trademark of Linear Technology Corporation. No RSENSE is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective ■ Portable Instruments owners. Protected by U.S. Patents, including 5481178, 5731694, 5929620, 6144194, ■ Distributed DC Power Systems 6580258, 5994885 UTYPICAL APPLICATIOEfficiency and Power Loss vs Load Current VIN 2.75V TO 100 10000 187k 9.8V M1 2.2µH 95 EFFICIENCY SW1 SENSE1+ VOUT1 59k V V 2.5V OUT = 2.5V FB1 PVIN1 + 90 1000 POWER LOSS (mW) D1 47 I µF TH1 PGATE1 85 15k 10µF V 220pF PGOOD VIN ×2 OUT = 1.8V LTC3737 80 100 SGND PGND 220pF TRACK RUN/SS 75 15k 47µF EFFICIENCY (%) I PGATE2 D2 + TH2 70 TYPICAL POWER LOSS 10 59k VFB2 PVIN2 2.2µH VOUT2 (VOUT = 2.5V) SW2 SENSE2+ 1.8V 65 M2 118k VIN = 3.3V 60 1 3737 F01 1 10 100 1000 10000 LOAD CURRENT (mA) Figure 1. High Efficiency, 2-Phase, 550kHz Dual Step-Down Converter 3737 F01b 3737fa 1
