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?

There is no land pattern drawing for the CP-28-12 package to be found anywhere!