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powering AD5700 with AD5421

Question asked by frankd on Aug 14, 2014
Latest reply on Aug 18, 2014 by DRice



I am Powering AD5700 with AD5421. I am trying to determine the best way to power the AD5700 from the AD5421. My
design is isolated and the isolation is inefficient so current draw is a consideration.
I am sourcing 5V from REGout to a linear 3.5V regulator and that powers an
isolated power supply that feeds to a ADuCM361. I have a ADUC1441 isolator that
allows SPI communication from the MCU to the AD5421.
I see 3 ways to power the AD5700, the IOVdd of the AD5421, and the isolator:
1. Use the 3.5V linear regulator. This most closely matches the Hart registered
design but consumes the most power.
2. Use the 3.3V DVdd of the AD5421
3. Use the 2.5V reference from the AD5421
Do you see any issues with the last two choices?

Thank you,