POWER LOSS (W) LTC3772 Micropower No R SENSE Constant Frequency Step-Down DC/DC Controller FEATURES DESCRIPTIO No Current Sense Resistor Required The LTC 3772 is a constant frequency current mode 40A No-Load Quiescent Current step-down DC/DC controller in a low profile 8-lead SOT-23 TM High Output Currents Easily Achieved (ThinSOT ) and a 3mm 2mm DFN package. The No TM Internal Soft-Start Ramps V R architecture eliminates the need for a current OUT SENSE Wide V Range: 2.75V to 9.8V sense resistor, improving efficiency and saving board IN Low Dropout: 100% Duty Cycle space. Constant Frequency 550kHz Operation The LTC3772 automatically switches into Burst Mode Low Ripple Burst Mode Operation at Light Load operation at light loads to increase efficiency at low output Output Voltage as Low as 0.8V current. It consumes only 40A of quiescent current 1.5% Voltage Reference Accuracy under a no-load condition. Current Mode Operation for Excellent Line and Load The LTC3772 incorporates an undervoltage lockout fea- Transient Response ture that shuts down the device when the input voltage Only 8A Supply Current in Shutdown falls below 2V. To maximize the runtime from a battery Low Profile 8-Lead SOT-23 (1mm) and source, the external P-channel MOSFET is turned on (3mm 2mm) DFN (0.75mm) Packages continuously in dropout (100% duty cycle). High switch- U APPLICATIO S ing frequency of 550kHz allows the use of a small inductor and capacitors. An internal soft-start smoothly ramps the 1- or 2-Cell Li-Ion Battery-Powered Applications output voltage from zero to its regulation point. Wireless Devices , LTC and LT are registered trademarks of Linear Technology Corporation. Portable Computers Burst Mode is a registered trademark of Linear Technology Corporation. ThinSOT and No R are trademarks of Linear Technology Corporation. SENSE Distributed Power Systems All other trademarks are the property of their respective owners. TYPICAL APPLICATIO 550kHz Micropower Step-Down DC/DC Converter Efficiency and Power Loss vs Load Current 100 10 680pF 20k V = 3.3V IN V IN I /RUN V TH IN 90 2.75V TO 9.8V V = 5V 1 LTC3772 IN 10F 80 GND PGATE 3.3H 82.5k V OUT 0.1 70 V 2.5V SW FB V = 5V IN 2A V = 3.3V IN 47F 60 22pF 174k 0.01 3772 TA01 50 FIGURE 5 CIRCUIT 40 0.001 1 10 100 1000 10000 LOAD CURRENT (mA) 3772 TA01b 3772f 1 EFFICIENCY (%) U ULTC3772 ABSOLUTE MAXIMUM RATINGS (Note 1) Input Supply Voltage (V )........................ 0.3V to 10V Operating Temperature Range (Note 2) .. 40C to 85C IN IPRG, PGATE Voltages ................ 0.3V to (V + 0.3V) Junction Temperature (Note 3)............................ 125C IN V , I /RUN Voltages ............................. 0.3V to 2.4V Storage Temperature Range ................. 65C to 125C FB TH SW Voltage ........... 2V to (V + 1V) or 10V Maximum Lead Temperature (Soldering, 10 sec) IN PGATE Peak Output Current (<10s) ........................ 1A TSOT-23 ........................................................... 300C PACKAGE/ORDER INFORMATION ORDER PART ORDER PART TOP VIEW NUMBER NUMBER GND 1 8 PGATE TOP VIEW LTC3772EDDB LTC3772ETS8 V 2 7 V FB IN I 1 8 NC PRG 9 I /RUN SW I /RUN 2 7 SW 3 6 TH TH V 3 6 V FB IN I 4 5 NC PRG GND 4 5 PGATE DDB8 PART MARKING TS8 PART MARKING TS8 PACKAGE DDB PACKAGE 8-LEAD PLASTIC TSOT-23 8-LEAD (3mm 2mm) PLASTIC DFN LBNR LTBNQ T = 125C, = 230C/W JMAX JA T = 125C, = 76C/W JMAX JA EXPOSED PAD (PIN 9) IS GND MUST BE SOLDERED TO PCB Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The indicates specifications which apply over the full operating temperature range, otherwise specifications are at T = 25C. V = 4.2V unless otherwise noted. (Note 2) A IN PARAMETER CONDITIONS MIN TYP MAX UNITS Input Voltage Range 2.75 9.8 V Input DC Supply Current (Note 4) Normal Operation V /RUN = 1.3V 250 375 A ITH SLEEP Mode 40 60 A Shutdown V /RUN = 0V 8 20 A ITH UVLO V < UVLO Threshold 100mV 1 5 A IN Undervoltage Lockout (UVLO) Threshold V Rising 2.0 2.75 V IN V Falling 1.85 2.60 V IN Start-Up Current Source V /RUN = 0V 0.7 1.2 1.7 A ITH Shutdown Threshold (at I /RUN) V /RUN Rising 0.3 0.6 0.95 V TH ITH Regulated Feedback Voltage 0C T 85C (Note 5) 0.788 0.800 0.812 V A 40C T 85C (Note 5) 0.780 0.800 0.812 V A Feedback Voltage Line Regulation 2.75V V 9.8V (Note 5) 0.08 0.2 mV/V IN Feedback Voltage Load Regulation I /RUN = 1.6V (Note 5) 0.2 % TH I /RUN = 1V (Note 5) 0.2 % TH 3772f 2 U W U U WWW