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AMC3301-Q1: Common Mode Rejection

Part Number: AMC3311-Q1
Other Parts Discussed in Thread: AMC3330, AMC3311

Tool/software:

Hello Experts,

I have attached a snippet of the circuit here,

The idea is to measure the DC voltage which unfortunately, has a common mode component in it. The measurment works, but we do see the common mode component, causing unnecessary peaks trigerring some of the sfatey and other functions.

Here is the Commom mode rejection test setup and results



ideally I do not expect to see the 500V pulses at the output, since the IN and HGND pins are shorted before the resisitor divider, unfortunately following are the results (900mVp-p)




The green signal is the input,
Pink is measured at the analog output of AMC and yellow is measured after the OpAmp circuit that is a second order low pass filter+10 X amplitude.

I noticed that the datasheet of AMC3311 does not mention the CMRR values unlike AMC3330, which we chose for the AC voltage measurment.


We performed similar test on the evaluation board of AMC3330

following are the results

The output is 280mVp-p but still we see the common mode voltage component..

What exactly am I doing wrong?, any help is much appreciated.

Thank you