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ADS1299 Frequency Plot

INg
Genius 3475 points
Other Parts Discussed in Thread: ADS1299

HI

Is there anyway i can get a ADS1299 ADC frequency response plots? Base on Max. PGA gain setting of 24.

We want plots on both 250Hz and 500Hz sample rate (output data rate). 

Is there a SNR plot for 100Hz signal for sampling rate at 250 & 500Hz ?

  • 0
    TI__Mastermind 38745 points
    Hey Ivan,

    The frequency response for the ADS1299 digital filter is described by Equation 4 in the datasheet. For 250 SPS you can substitute 4096 in for N and for 500 SPS you can substitute 2048. Images of the response are shown collectively in figures 25 through 29 inclusive. This is a digital filter so the response is guaranteed by a logic circuit.

    Figure 13 shows a 60 Hz signal SNR plot for the 16 kSPS data rate. Noise performance will be better at the lower data rates because more of the band will be filtered. I can collect that exact data for you if you wish.

    Regards,
    Brian Pisani
  • 0 in reply to Brian Pisani
    Genius 3475 points

    HI Brian

    THanks again for the help extended. I would appreciate very much if you could help to collect the exact plots 

    BR

    Ivan

  • 0 in reply to INg
    TI__Mastermind 38745 points

    Hey Ivan,

    See the attached plots of data taken with the EVM. In each case I set the PGA gain to 24, held IN1N at mid-supply, and input a 100 mVp 100 Hz signal using a signal generator in the lab to IN1P. I captured the data to a text file using the EVM, imported it to MATLAB. I windowed the data with a Blackman-Harris window and I used the fft function to perform a DTFT on the data. The attached files show plots of the result.

    Regards,

    Brian Pisani

    250sps.pdf

    500sps.pdf

  • 0 in reply to Brian Pisani
    Genius 3475 points
    Hi Brian,

    Thanks very much for your support.
    Could i trouble you for a couple more plots

    provide the peak magnitude value (dB) for:
    (a) 65Hz at 250sps and 500sps
    (b) 100Hz at 250sps and 500sps

    Ivan
  • 0 in reply to INg
    TI__Mastermind 38745 points
    Hey Ivan,

    These peak magnitudes will be determined by the digital filter which you can model as a standard third order averaging filter. There is no need to collect data to determine them. I can calculate the ones you requested:

    (a) At 250 SPS: -2.97 dB, At 500 SPS: -0.73 dB
    (b) At 250 SPS: -7.23 dB, At 500 SPS: -1.73 dB

    Regards,
    Brian PIsani