there any spike to expect??
The ADuM1200 only draws significant current from the supplies at each logic
transition. This is why the Idd1, Idd2 vs frequency curves are linear above
1Mbps which is the minimum. See also page 15 of the datasheet.
Therefore the customer can expect to see a current pulse in the supplies
simultaneous with the input and output logic transition, and a low supply
current at other times. Using the recommended power supply decoupling will
reduce the slew rate and amplitude of the current pulse, since the decoupling
capacitor will supply some of the current requirements.