ADuM140x: power only one side
From the datasheet:


  Unlike other optocoupler alternatives, the ADuM1400/ADuM1401/ADuM1402 isolators have a patented refresh feature that ensures dc correctness in the absence of input logic transitions and when power is not applied to one of the supplies.




Since you haven't provide a schematic (at this time) I can't comment as to what will happen in your case.