This power supply electronic circuit is based on the ADP1864 is constant-frequency, current-mode, step-down dc-to-dc controller. The ADP1864 drives a P-channel MOSFET that regulates an output voltage as low as 0.8 V with ±1.25% accuracy, for up to 5 A load currents, from input voltages as high as 14 V.

The ADP1864 allow accurate setting of the current limit with an external resistor, and the output voltage is easily adjustable using two external resistors. The ADP1864 includes an internal soft start to allow quick power-up while preventing input inrush current. Additional safety features include short-circuit protection, output overvoltage protection, and input undervoltage protection. Current-mode control provides fast and stable load transient performance, while the 580 kHz operating frequency allows a small inductor to be used in the system.
The maximum output voltage that can be provided using this regulator is from 0.8 volts up to input voltage .
Using this circuit diagram you will have at the output  a 3.3 volts at a maximum current of 2 amperes . Also this circuit has a high efficiency up to 94% and is pin to pin compatible with LTC1772 and LTC3801 integrated circuits manufactured by Linear Technology .