AD5623R Power-on Reset Circuit

Hi,

Please give me more information about the power-on reset circuit of AD5623R.

1) What is the start Vdd voltage of power-on reset?
2) Must it always be started up from 0 V for the power-on reset?
   Is there any requirements or margin?
3) Is there other requirements for the power-on reset?
   If the requirements is not followed, what is the output voltage?

Best regards,
Nikkee