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3 Phase Power meter reference design violates isolation?

Question asked by AdilM on Jun 23, 2016
Latest reply on Jun 24, 2016 by dlath

Im looking at a few ways to design a 3 phase power meter and all the different isolated topologies involved.

 

Recently i came across this Analog Devices application note highlighting a isolated design; however i do not understand why they tie the digital ground of the MCU and ADC to the neutral (GND_MCU) when i believe it is supposed to be isolated from the mains? Wouldnt a better design simple derive a some floating power supply to power the digital (upper) side of the circuit?

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The whole document is here:Reference app note

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