LTC3772EDDB#TRPBF

LTC3772 Micropower No RSENSE Constant Frequency Step-Down DC/DC Controller U FEATURES DESCRIPTIO ■ The LTC®3772 is a constant frequency current mode step-down DC/DC controller in a low profile 8-lead SOT-23 (ThinSOTTM) and a 3mm × 2mm DFN package. The No RSENSETM architecture eliminates the need for a current sense resistor, improving efficiency and saving board space. ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ No Current Sense Resistor Required 40µA No-Load Quiescent Current High Output Currents Easily Achieved Internal Soft-Start Ramps VOUT Wide VIN Range: 2.75V to 9.8V Low Dropout: 100% Duty Cycle Constant Frequency 550kHz Operation Low Ripple Burst Mode® Operation at Light Load Output Voltage as Low as 0.8V ±1.5% Voltage Reference Accuracy Current Mode Operation for Excellent Line and Load Transient Response Only 8µA Supply Current in Shutdown Low Profile 8-Lead SOT-23 (1mm) and (3mm × 2mm) DFN (0.75mm) Packages The LTC3772 automatically switches into Burst Mode operation at light loads to increase efficiency at low output current. It consumes only 40µA of quiescent current under a no-load condition. The LTC3772 incorporates an undervoltage lockout feature that shuts down the device when the input voltage falls below 2V. To maximize the runtime from a battery source, the external P-channel MOSFET is turned on continuously in dropout (100% duty cycle). High switching frequency of 550kHz allows the use of a small inductor and capacitors. An internal soft-start smoothly ramps the output voltage from zero to its regulation point. U APPLICATIO S ■ ■ ■ 1- or 2-Cell Li-Ion Battery-Powered Applications Wireless Devices Portable Computers Distributed Power Systems , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. ThinSOT and No RSENSE are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. U ■ TYPICAL APPLICATIO Efficiency and Power Loss vs Load Current 550kHz Micropower Step-Down DC/DC Converter 10 100 20k LTC3772 3.3µH SW 47µF 22pF VIN = 5V 10µF PGATE 82.5k VFB 90 VOUT 2.5V 2A 1 80 0.1 70 VIN = 5V VIN = 3.3V 60 174k POWER LOSS (W) GND VIN = 3.3V VIN 2.75V TO 9.8V VIN ITH/RUN EFFICIENCY (%) 680pF 0.01 3772 TA01 50 FIGURE 5 CIRCUIT 40 1 100 1000 10 LOAD CURRENT (mA) 0.001 10000 3772 TA01b 3772f 1 LTC3772 U W W W ABSOLUTE MAXIMUM RATINGS (Note 1) Input Supply Voltage (VIN)........................ – 0.3V to 10V IPRG, PGATE Voltages ................ – 0.3V to (VIN + 0.3V) VFB, ITH/RUN Voltages ............................. – 0.3V to 2.4V SW Voltage ........... – 2V to (VIN + 1V) or 10V Maximum PGATE Peak Output Current (