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current sensor circuit grounded to digital plane?

Question asked by markushug on Apr 7, 2016
Latest reply on Apr 18, 2016 by dlath

Hi all,

 

in Application Note AN639 (ADE Products: FAQs), I think there is a mistake in the statement to ground plane considerations:

 

What are the considerations for designing the ground

plane on an energy meter PCB?

From the PCB designer’s standpoint, analog ground (AGND)

and digital ground (DGND) pins of the ADE IC should be tied

together outside the chip with the lowest impedance connection

possible. They are not connected within the chip because the

noise present in the digital channel might enter the analog

circuitry and affect its performance. Thus, when they are tied

together outside the chip, they must be connected to the analog

ground plane of the system. All the other circuitry, such as

current sensor circuit, crystal oscillator circuit, and the

microcontroller, must be grounded to the digital plane of 

the system. 

(AN639, Rev. A, Page 6 of 16)

 

I can't believe that the current sensor circuit must be grounded to the digital plane since it is one of the most important analog parts of the meter and quite contrary it should be essential to separate it from the noisy digital parts like crystal and microcontroller stuff.

Please clarify. Thank you!

 

Best Regards

Markus

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