Features

• Wide Input Voltage Range: 3.6V to 34V Operating, 36V Maximum
• 2A Maximum Output Current
• Low Ripple Burst Mode Operation
   50µA IQ at 12VIN to 3.3VOUT
   Output Ripple < 15mVP-P
• Adjustable Switching Frequency: 300kHz to 2.8MHz
• Low Shutdown Current: IQ < 1µA
• Integrated Boost Diode
• Integrated Power Schottky Diode
• Power Good Flag
• Saturating Switch Design: 0.18Ω On-Resistance
• 1.265V Feedback Reference Voltage
• Output Voltage: 1.265V to 20V
• Soft-Start Capability
• Small 14-Pin Thermally Enhanced (4mm x 3mm) DFN Package

Typical Application

Description

The LT3681 is an adjustable frequency (300kHz to 2.8MHz) monolithic buck switching regulator that accepts input voltages up to 34V (36V maximum). A high efficiency 0.18O switch is included on the die along with a boost Schottky diode and the necessary oscillator, control, and logic circuitry. An undedicated power Schottky diode is integrated into the LT3681 to minimize the solution size. Current mode topology is used for fast transient response and good loop stability. Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping output ripple below 15mV in a typical application. In addition, the LT3681 can further enhance low output current efficiency by drawing bias current from the output when VOUT is above 3V. Shutdown reduces input supply current to less than 1µA while a resistor and capacitor on the RUN/SS pin provide a controlled output voltage ramp (soft-start). A power good flag signals when VOUT reaches 90% of the programmed output voltage. The LT3681 is available in 14-Pin 4mm x 3mm DFN package with exposed pads for low thermal resistance.