The MCP1603 is a high efficiency fully integrated 500 mA 2.0 MHz synchronous buck regulator ideally suited for Li-Ion/NiMH Battery powered application powered. At heavy loads, the MCP1603 operates in the 2.0 MHz fixed frequency PWM mode which provides a low noise, low output ripple, small-size solution. When the load is reduced to light levels, the MCP1603 automatically changes operation to a PFM mode to minimize quiescent current draw from the battery. No intervention is necessary for a smooth transition from one mode to another. These two modes of operation allow the MCP1603 to achieve the highest efficiency over the entire operating current range.