Does anybody knows where i could find an example schematics for the right way to connect the USB connector to a kinetis MK20DX when the device is self powered ? I am mostly concern to have the circuit protected when the board is connected to the USB port of a host which has power but my board it self is not powered. I have 2 prototypes board that have been damage when the board USB is connected to a PC before I give power to the board. If the board is powered before being connected to the PC USB is OK (have been using the boards for days but USB stop working and the chip got hot when doing the sequence I think damage the USB ). For reference I am currently using the following circuit to connect the USB to the MCU .