A buck converter, also known as a step-down converter, is a DC/DC power converter that provides voltage step down and current step up. The converter reduces the voltage when the power source has a higher voltage than Vin. A buck converter generally provides the most efficient solution with the smallest external components.
Unsure if a low powered linear regulator or highly efficient switching regulator is a better option for your design? Learn more about?Linear vs. Switching Regulators.