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low end cut off frequency of AFE4403

david sun77114
Expert 2162 points
Other Parts Discussed in Thread: AFE4403

Hello,

In our application, we need the low end cut off frequency down to 0.5 Hz. could you please tell me what is the frequency response of AFE4403 at the low frequency end. is there a way to adjust the filter to change the frequency response.

Sincerely,

David Sun

  • 0
    TI__Mastermind 49956 points
    Hi David,

    Can you elaborate on the application that requires the cut off freq. of 0.5 Hz?

    The low pass filter corner frequency of the switched RC filter is 500 Hz. But the effective bandwidth of the filter is also dependent on the sampling duty cycle (active sampling time). When the duty cycle reduces, the effective bandwidth of the filter reduces.
    For example, with 5% sampling duty cycle, the effective signal bandwidth is 25 Hz.
  • 0 in reply to Praveen Aroul
    Expert 2162 points
    Hi Praveen
    We have a medical application that will detect breath rate. we have a TI 24 Bit ADC solution which works fine. but when we use this AFE4403, we lost the low frequency components of the signal. I wonder is the AFE4403 work like a band-pass filter, it will cut the low frequency components lower than 0.5Hz. anyway, do you have a frequency response chart of AFE4403 at 500 sps or 250 sps. which can show the bandwidth of AFE4403.
    Sincerely,

    David Sun
  • 0 in reply to david sun77114
    TI__Mastermind 49956 points
    Hi David,

    As I mentioned earlier, the effective bandwidth of the switched RC filter is dependent on both the PRF and the sampling time (sampling duty cycle). Figure 10 of the AFE4403 datasheet illustrates the baseband response of the RC filter for a 5% and 25% duty cycle.

    Regarding the signal, did you run the FFT on the signal to look at the frequency components? Are you seeing a bandpass response?
    Could you attach the raw data from the AFE that exhibits this behavior?