3.3 Power Sources
The SAM R21 Xplained Pro kit can be powered by several power sources as listed in the table below.
| Power input | Voltage requirements | Current requirements | Connector marking |
|---|---|---|---|
| External power | 5V ±2% (±100mV) for USB host operation. 4.3V to 5.5V if USB host operation is not required. | Recommended minimum is 1A to be able to provide enough current for connected USB devices and the board itself. Recommended maximum is 2A due to the input protection maximum current specification. | PWR |
| Embedded debugger USB | 4.4V to 5.25V (according to USB spec.) | 500mA (according to USB spec.) | DEBUG USB |
| Target USB | 4.4V to 5.25V (according to USB spec.) | 500mA (according to USB spec.) | TARGET USB |
The kit will automatically detect which power sources are available and choose which one to use according to the following priority:
- External power.
- Embedded Debugger USB.
- Target USB.
Info: External power is
required when 500mA from a USB connector is not enough to power the board with
possible extension boards. A connected
USB device in a USB host application might easily exceed this limit.