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AD8232 outputting a noise

Question asked by Astralist on Nov 1, 2016

Hello, i've been designing a device for measuring rats ECG using AD8232, but as the board completed, i'm observing these strange phenomenon:

 

The output is constantly changes, it just like the ad8232 only amplifying a noise (note that these are two ad8232).

Signal swings from 0 to 3.3V (i used REFOUT as reference).

As you can see the swings of the waveform, the green one mostly saturated at 0V while the blue one mostly saturated at 3.3V

 

The output from IAOUT when the lead is disconnected or when the input is shorted is about 1.5V, is that even normal?

I just follow the sample from the datasheet but with different HPF and with total G=200 referenced at 1.65V from REFOUT, please take a look at the schematic below:

 

 

Here is the PCB layout, for reference:

 

Please  help!

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