The USB 2.0 mini B receptacle is connected to the ATxmega128B1 to demonstrate the USB device feature of the product.
The onboard LDO regulator and the LCD backlight are powered by V_BUS.
D+ & D- are connected to the microcontroller, powered directly thru VTG. So the USB interface only operates if the ATxmega128B1 is powered with VTG at 3.3V.