I want to use the AD7768-1 with 5V AVDD1 = Vref and 3,3V VDDIO. In demo-circuits the AVDD2 is connected to probably noisy VDDIO!Wouldn't it be better to supply AVDD2 from 5V over a R-C-Filter, that would lower the voltage to around 3V?
Additionally:There is no land pattern drawing for the CP-28-12 package to be found anywhere!
Firstly Page 80 of the Data sheet has the land pattern drawing, let me know what is the detail you need?
On supply recommendations i am not sure which reference design are you referring to in your query, the evaluation board schematic has the supply rails separated