CNVST pin of LTC2389-16

Hi, 

I would like to ask a question about  CNVST pin on LTC2389.

The datasheet says the pin CNVST's logic level is determined by VDD, not OVDD. But the demo schematic on page 37 shows the CNVST is drived by a 3.3V signal, means its logic level is determined by OVDD. Which one is correct, OVDD or VDD?

Thanks!