I am designing a board that will be a power pass-through for 18V and 5V. I am using a separate power supply for each voltage. The outputs are from each supply are floating.
When plugged into the board, they will share common copper on the return lead. Is this OK? Is there a preferred way to do this?
In my view the GND will be common from the input supply .....this is common when you have multiple power derivation.....I don't see any harm for the board.....but if you really fell that you need to have protection for 18v and 5V use split plane connection and will have common connection made with inductor in series....However this technique is unique for chasis Ground and system ground connection.....
In my view there will not be any harm even you use same return path for both 5v and 18v....as voltage levels are also comparable ....but in case you are using 18 v and a ddr2 application like 1.8v then I would have been recommanded definatly...split plane....