Power Supply Connections?

Thread Starter


Joined Nov 27, 2009
I am working on this project where there is an FDTI for USB to UART communication with a computer. The microcontroller I am using is an atmega2560.

I am trying to design a power supply switching circuit which the boards I am making will either get +5V from the USB connection or +5V from a computer power supply (because I am also working with +12V for motor controls). Is it alright if both the USBVCC and the power supply +5V is connected on the same rail? If not, is there a good way of switching which VCC to connect to the board's VCC rails?

If USBVCC is only connected, then connect it to the board rail. Same for the power supply.
If both USBVCC and power supply are connected, only choose the power supply?

Any advice or suggestion will be helpful, thanks


Gate CMD is just another method of power (from a barrel jack connector). I essentially used the arduino Atmega2560 schematic reference. So Gate CMD will be 0V if there is no power coming from jack connector, thus allowing USBVCC to power through

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