In the evaluation board for AD9522, separate power supplies are used for Vs and Vcp.
Is it mandatory?
Can I power both the supplies from a single LDO - ADP3339.
you can use a single 3.3V supply as the data sheet does not indicate VCP should be supplied from a separate LDO.
I see ADP3339 is not recommended for new designs, so a conservative approach for you would be to select another LDO.