4.1 Power Distribution

ATmega4809 Xplained Pro has two power sources as described in Power Sources. The block diagram below shows the power supply circuitry on the board. The kit can be powered by the EDBG USB and an external 5.0V source. The kit will automatically select which source to draw power from. ATmega4809 can be powered by 3.3V (regulated) or 5.0V (USB/external voltage). The voltage is selectable using a jumper on the power selection header J105.

An on-board power switch is used to turn power to the ATmega4809 ON and OFF. This power switch is controlled by the EDBG. When the kit is powered up, the EDBG reads the ID chip information from all connected Xplained Pro extension boards and checks that they are compatible with the voltage selected by the power selection header J105. If the selected voltage is within the connected extensions ranges, the switch will open. If not, the EDBG power LED will blink rapidly and the switch will stay closed resulting in no power provided to ATmega4809, the on-board peripherals, and the connectors.

CAUTION: As ATmega4809 Xplained Pro can be powered by 5.0V, care must be taken not to connect any Xplained Pro extensions that do not support this voltage, doing so may result in permanent damage. Check the respective extension kit's user guide to see which voltages are acceptable.

Info: The EDBG reads the ID information from Xplained Pro extensions and controls the power switch when the kit is powered up. This mechanism does not check hot-plugging of extension boards.