In the input， just has 3.3V power supply for VDDP, VDD1 can connect to VDDP or not？
From the datasheet of Adum5411, said theVDD1 can connect to VDDP.
The supply inputs for the digital isolation and dc/dc converter are independent. They can be connected to different supplies or the same supply.
If this application has a single 3.3V supply rail, it sounds like there is only one option available - connect both VDD1 and VDDP to the same supply rail.