POWER LOSS (W) LT3681 36V, 2A, 2.8MHz Step-Down Switching Regulator with Integrated Power Schottky Diode FEATURES DESCRIPTIO Wide Input Voltage Range: 3.6V to 34V Operating, The LT 3681 is an adjustable frequency (300kHz to 2.8MHz) 36V Maximum monolithic buck switching regulator that accepts input 2A Maximum Output Current voltages up to 34V (36V maximum). A high ef ciency Low Ripple Burst Mode Operation 0.18 switch is included on the die along with a boost 50A I at 12V to 3.3V Schottky diode and the necessary oscillator, control, and Q IN OUT Output Ripple < 15mV logic circuitry. An undedicated power Schottky diode is P-P Adjustable Switching Frequency: 300kHz to 2.8MHz integrated into the LT3681 to minimize the solution size. Low Shutdown Current: I < 1A Current mode topology is used for fast transient response Q Integrated Boost Diode and good loop stability. Low ripple Burst Mode operation Integrated Power Schottky Diode maintains high ef ciency at low output currents while Power Good Flag keeping output ripple below 15mV in a typical application. Saturating Switch Design: 0.18 On-Resistance In addition, the LT3681 can further enhance low output 1.265V Feedback Reference Voltage current ef ciency by drawing bias current from the output Output Voltage: 1.265V to 20V when V is above 3V. Shutdown reduces input supply OUT Soft-Start Capability current to less than 1A while a resistor and capacitor on Small 14-Pin Thermally Enhanced the RUN/SS pin provide a controlled output voltage ramp (4mm x 3mm) DFN Package (soft-start). A power good ag signals when V reaches OUT 90% of the programmed output voltage. The LT3681 U APPLICATIO S is available in 14-Pin 4mm x 3mm DFN package with exposed pads for low thermal resistance. Automotive Battery Regulation , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Power for Portable Products Burst Mode is a registered trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Distributed Supply Regulation Industrial Supplies Wall Transformer Regulation TYPICAL APPLICATIO 5V Step-Down Converter Ef ciency V V 100 10.0000 IN OUT 6.3V TO 5V 90 34V 2A V BD IN 80 1.0000 RUN/SS BOOST OFF ON 70 0.47 F L 6.8 H 60 20k 0.1000 V SW C LT3681 4.7 F 50 DC 40 0.0100 RT DA 30 330pF V = 12V IN PG BIAS 20 0.0010 V = 3.3V OUT 590k L = 4.7 H 10 60.4k FB GND F = 800 kHz 0 0.0001 200k 22 F 0.0001 0.001 0.01 0.1 1 10 I (A) LOAD 3681 TA01b 3681 TA01 L: NEC PLC-0745-6R8 3681f 1 EFFICIENCY (%) U ULT3681 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW V , RUN/SS Voltage .................................................36V IN PG 1 14 RUN/SS BOOST Pin Voltage ...................................................56V BIAS 2 13 V IN 15 BOOST Pin Above SW Pin .........................................30V FB 3 12 SW FB, RT, V Voltage .......................................................5V C GND 4 11 BOOST BIAS, PG, BD Voltage ................................................30V V 5 10 BD C R 6 9 DC T 16 Maximum Junction Temperature .......................... 125C GND 7 8 DA DC above DA .............................................................40V DE14MA PACKAGE Operating Temperature Range (Note 2) 14-LEAD (4mm 3mm) PLASTIC DFN LT3681E ............................................... 40C to 85C T = 125C, = 43C/W JMAX JA EXPOSED PAD (PIN 15) IS GND, MUST BE SOLDERED TO PCB Storage Temperature Range ................... 65C to 150C EXPOSED PAD PIN 16 IS DC ORDER PART NUMBER DE PART MARKING LT3681EDE 3681 Order Options Tape and Reel: Add TR Lead Free: Add PBF Lead Free Tape and Reel: Add TRPBF Lead Free Part Marking: