I want to measure full AC mains voltage with let's say 100ksps, 240Vrms and I plan to use a resistive divider 1/100. From my understanding, this means +/-Vp = +/- 340V or after divider +/- 3.4V.
ADC will be powered from a isolated brick.
I'm not clear how to properly configure (hardware and software) the ASD8681 for high voltage AC measurements. This device appear to be a Pseudo-Differential True Bipolar (image from LT)
https://www.ti.com/lit/gpn/ADS8689
In the datasheet, it says that one of bipolar range can be +/-5.12V and this seems to be most convenient to me.
What is not clear is related to input impedance.
They say that it's about 1M and so, allowing to use directly (without OA) in some cases. But in my case, resistive divider should be high enough to not draw significant power. A 1M total resistance will dissipate 160mW at 400V which is acceptable. But this will also make a big low pass filter to the input right?
It is ok to hook divider directly to the ADC input?
Another question is related to AIN_GND
They say
In order to maintain the dc accuracy of the system, matching the external source impedance on the AIN_P input pin with an equivalent resistance on the AIN_GND pin is recommended. This matching helps cancel any additional offset error contributed by the external resistance.
What should I understand from this? Add also 10K from this pin to GND ?
(suppose my divider is 1M//10k)
