LT3481 36V, 2A, 2.8MHz Step-Down Switching Regulator with 50µA Quiescent Current FEATURESDESCRIPTION ■ Wide Input Range: 3.6V to 34V Operating, The LT®3481 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 effi ciency ■ Low Ripple Burst Mode® Operation 0.18Ω switch is included on the die along with a boost 50μA IQ at 12VIN to 3.3VOUT Schottky diode and the necessary oscillator, control, and Output Ripple < 15mV logic circuitry. Current mode topology is used for fast ■ Adjustable Switching Frequency: 300kHz to 2.8MHz transient response and good loop stability. Low ripple ■ Low Shutdown Current: IQ < 1μA Burst Mode operation maintains high effi ciency at low ■ Integrated Boost Diode output currents while keeping output ripple below 15mV ■ Power Good Flag in a typical application. In addition, the LT3481 can fur- ■ Saturating Switch Design: 0.18Ω On-Resistance ther enhance low output current effi ciency by drawing ■ 1.265V Feedback Reference Voltage bias current from the output when VOUT is above 3V. ■ Output Voltage: 1.265V to 20V Shutdown reduces input supply current to less than 1μA ■ Soft-Start Capability while a resistor and capacitor on the RUN/SS pin provide a ■ Synchronizable Between 275kHz to 475kHz controlled output voltage ramp (soft-start). A power good ■ Small 10-Pin Thermally Enhanced MSOP and fl ag signals when VOUT reaches 90% of the programmed (3mm x 3mm) DFN Packages output voltage. The LT3481 is available in 10-Pin MSOP and 3mm x 3mm DFN packages with exposed pads for APPLICATIONS low thermal resistance. L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered ■ Automotive Battery Regulation trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. ■ Power for Portable Products ■ Distributed Supply Regulation ■ Industrial Supplies ■ Wall Transformer Regulation TYPICAL APPLICATION3.3V Step-Down ConverterEffi ciency VIN VOUT 90 10000.0 4.5V TO 3.3V 34V 2A VIN BD 80 1000.0 OFF ON RUN/SS BOOST POWER LOSS (mW) 0.47μF 70 100.0 16.2k 4.7μH V LT3481 SW C 4.7μF 60 10.0 RT 330pF EFFICIENCY (%) 50 1.0 PG BIAS VIN = 12V 324k V 60.4k FB 40 OUT = 3.3V 0.1 GND L = 4.7μ F = 800 kHz 200k 22μF 30 0.01 0.0001 0.001 0.01 0.1 1 10 LOAD CURRENT (A) 3481 TA01 3481 TA01b 3481fc 1
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