Firebeetle 32e Simultaneous USB and VCC power

I am using a Firebeetle 32E in a project and am providing regulated 5v to VCC and it is working fine.   My application does not use a battery.   The USB is normally disconnected.

Occasionally I need to update the firmware by programming the board using the USB connection.  What I am doing now is disconnecting the 5V VCC power first to avoid damaging the board.  Is this necessary or is there protection circuitry to prevent damage when simultaneously powering the board from Both USB and 5V VCC?

Thanks in advance.