All power sources for the Intel Joule expansion board are routed into a multiplexer device, U18.
The power mux defaults to +VDC_IN when both +VDC_IN and +VBUS are present. Refer to the manufacturer's datasheet for input impedance, current limit details, and low voltage lock-out specifications.
When it is booted, it is not possible to switch between power input sources without rebooting the platform, because the power mux is a break-before-make connection.
The power mux passes the selected output onto the +VIN_CHRG bus, which is routed to the PMIC device, EU2. The battery management features of EU2 are not supported. See Battery Path for details.
Voltage regulators and load switches on the expansion board provide the necessary supplies for various devices and interfaces of the board to function.