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
(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!