Delta Sigma Noise

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AlVa_264671
Level 5
Level 5
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Hi Every One !

   

 

   

I would need some help regarding noise generated for the Delta sigma in single end configuration.

   

As you can see in the schematic as result of array scanning I am geting pulses which votage depend of the pressure applied to every cell in the array.  My Vdda is 3.3 v . The issue is that with no pulse, ( checked with osciloscope) there is noise that  you can watch in the graphic display picture.

   

The only way to avoid that is using a PGA before the Delta sigma..

   

I cannot undestan that. !!!!

   

And even using a PGA,  I need to filter trough  code , like high pass filter values above 0x80, wich represent almost a half of the ADC range.

   

I woul appreciate very much any help.

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