Main Voltage Regulator

Main VREG can be supplied by two different voltage regulators; an LDO regulator and a buck switching regulator. The buck regulator will consume the least amount of power, having the highest efficiency of the two. The buck regulator does however require an inductor to be connected to the device. Since this inductor is not guaranteed to be available in all designs, SAM L21 will by default start from the LDO regulator. Switching between LDO and buck regulator is done by writing to the Voltage Regulator Selection bit in the Voltage Regulator System Control register (VREG.SEL) in the Supply Controller (SUPC).