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AD7714YN: Power up sequence

I have designed a circuit using a AD7714YN. I have +5V applied to DVDD and
+3.3V to AVDD. From the information given in the Rev-C data sheet I assumed
this to be OK. However, I am seeing now something like +4.2V on the AVDD pin
instead of the expected +3.3V. If I remove the AD7714YN from the circuit I get
3.3V at that pin, i.e. it looks like the higher voltage is somehow feeding
through internally. Could you please confirm that I can indeed power the
AD7714YN with AVDD=3.3V and DVDD=5.0V.


AVDD and DVDD must be within 0.3V of each other. 

The AD7714Y can not be operated under the conditions below because the ESDn
protection for the buffer and standby pins is to the Analog supplies, so if the
voltage on Avdd was lower than Dvdd, the diodes on these pins would turn on if
their voltage was greater than Avdd+0.7.