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ADS1291 noise problem

Other Parts Discussed in Thread: ADS1291

Hi

In our design we use single lead ecg reading using ads1291 ; when the system powered from the battery only we can read nice ecg from the human body ; when we power it from 220VAC ( power supply ) the ECG change to strange signal . we are using low pass filter 30 HZ FİR 30 taps   to remove 50hz .

please check the shematics ; could you advice us to solve the problem ?

Thank you in advanced   8105.ecg texas.PDF

  • Hi Hector,

    Your colleague, Sami, also contacted me. He explained that you are using a 30-tap FIR notch filter to eliminate the supply noise. Is this correct? Either way, I would imagine that the notch filter or a 30Hz LPF should eliminate most of the noise.

    When the board is powered by the 220VAC supply, how is that voltage stepped-down and converted to analog 3.3V? Perhaps you could use an LDO with higher PSRR at 50Hz.  If you view the output data in an FFT, does it show a large 50Hz noise component?

    Best Regards,