The power supply consists of a number of LDO and DC/DC regulators that maximize the system's power efficiency.
All system components are powered from the main on-chip voltage regulator VREGMAIN. The regulator converts the voltage supplied on VDD to internal voltage.
The device also has an USB regulator, which only powers the USB physical interface. It will not power the device. The USB regulator is documented in USBREG — USB regulator control.
The main supply voltage is connected to the VDD pin.