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Precision Data Converters
Precision Data Converters Forum
ADS131E08 line voltage sensing
I just got the COMBOSMARTMETER sample kit, and starting a design around the ADS131E08. My question is, is there more specific information about calculating "antialiasing RC filter" for input matching network. (Page 43 in datasheet)
Also suggested solution generating input bias via OPAMPIN/OPAMPOUT is missing some detail in the datasheet. Is there a more detailed application note?
Thanks for you support,
Generally, anti-alias filters are used to attenuate any "aliased" signals resulting from the sampling rate. So you would want a filter that rolls off after your frequency of interest (for power either 50/60Hz) and provide adequate attenuation at frequencies above fs/2.
Your circuit consideration must factor in to this since this filtering can also add phase delay, which can result in calculation errors for power factor and phase lead/lag parameters. This phase delay would need to be taken into account.
Regarding your question on the op-amp, what specifically are you interested that you cannot find in the datasheet? We will be glad to provide you with more information, just let us know what information you need.
Precision Data Converters
Thanks for your fast reply! I will follow your advice.
Page 43 shows how to set up internal op amp to generate the input bias. I was confused about "Rf". Since the internal op-amp is connected to (AVDD+AVSS)/2 I think Rf must be as small as 0 ohms. Am I right?
Is the internal op amp capable of driving all 8 inputs? I was planing to use a simple voltage divider to generate bias voltage. Is using the op amp recommended?
Rf can be as small as 0 ohms if you would like as it is the feedback resistor for the internal op amp.
The inputs to the converter are high impedance (you are looking into the PGA input) so you will have no problem driving multiple inputs with the internal op amp.
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