As given in Absolute maximum ratings,
VDD.....+0.3 to +6V
OVDD....-0.3V to the lower of (VDD + 0.3V) and +6V
A restriction arises between VDD and OVDD. Because the specification states that OVDD can be only a maximum of (VDD + 0.3)V, VDD must be powered up before or at the same time as OVDD. If OVDD was powered up first (say to 5 V), DVDD would be less than OVDD by 5 V at power-up and would therefore not comply with the Absolute Maximum Ratings and possibly damage the device.
So, delay the OVDD supply and power up VDD first. Same applies during power down as well. Power down OVDD first then VDD.