The SAM L21
supports a single or dual power supply from 1.62V to 3.63V. The same voltage must be
applied to both VDDIN and VDDANA.
The internal voltage regulator has four different modes:
- Linear mode: this mode does not require any external inductor. This is the default mode when CPU and peripherals are running
- Switching mode (Buck): the most
efficient mode when the CPU and peripherals are running.
- Low Power (LP) mode: This is the default mode used when the chip is in standby mode
- Shutdown mode: When the chip is in backup mode, the internal regulator is turned off
Selecting between switching mode and linear mode can be done by software on the fly, but the power supply must be designed according to which mode is to be used.