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ADS1192 - the extension of –3-dB BANDWIDTH

Hirotaka Matsumoto
Guru 27585 points
Other Parts Discussed in Thread: ADS1192

Hi all

Would you mind if we ask ADS1192?

We(our customer) would like to extend –3-dB BANDWIDTH without changing of "OUTPUT DATE RATE".
EX)  Reg   SPS[Hz]    BANDWIDTH[Hz]
         000    125           32.75 ---> 65.0
So, is it possible to only change "BANDWIDTH"(filter coefficient) using register setting?
(We could not find it on the datasheet.)

We need your help.

Kind regards,

Hirotaka Matsumoto

  • 0
    TI__Mastermind 38745 points
    Hello Matsumoto-san,

    It is impossible to change the filter coefficients on the digital decimation filter without changing the data rate.

    Regards,
    Brian Pisani
  • 0 in reply to Brian Pisani
    Guru 27585 points

    Brian san

    Thank you for your prompt reply!
    By the way, why is BANDWIDTH a quarter of OUTPUT DATA RATE?
    As our recognition, we guess that it is OK to use a half of OUTPUT DATA RATE.

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Mastermind 38745 points
    Hello Matsumoto-san,

    One of the core components of the delta-sigma topology is over sampling. The data output rate is not the sampling rate of the modulator. It is instead the decimated output of the digital averaging filter. For the ADS1192, the modulator samples at at 128 kHz and all of those points are pushed through the sinc3 filter which will essentially average the number of points specified by the OSR that is register programmed. If the output data rate is 125 SPS, the digital filter will have the response of a running 1024-point averaging filter. Only one of those 1024 points used the in average is output from the device. The -3dB point of that averaging filter is what dictates the output bandwidth.

    Regards,
    Brian Pisani
  • 0 in reply to Brian Pisani
    Guru 27585 points

    Brian san,

    Thank you for your prompt reply!

    Kind regards,

    Hirotaka Matsumoto