Please tell me the power start-up conditions required by AD9516-0.

My customers are using AD9516-0, and my customers are facing trouble.
Customers surveyed about their products and concluded that power supply and POR are suspicious.
Their products have a power supply that rises slowly.
The supply voltage rises to 2.9 V at several mS and then rises from 2.9 V to 3.3 V at about 100 mS.

Occasionally the product does not work normally.
The register setting from the serial interface is not reflected in the output.
A software-reset from the serial interface shows no effect.
Also, all the outputs at that time are fixed to high or low.
When L is input to the Reset terminal, the device will operate normally.

My customers are trying to remedy this problem.
Please tell me the power start-up conditions required by AD9516-0.

Best regards