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ADS 1258 Features

Talha Saleem
Intellectual 455 points
Other Parts Discussed in Thread: ADS1258, OPA365

hi,

    I am currently working on ADS1258. I wanted to know that How can a ADS1258 eliminate the need of a separate HPF and antialising filter before the
MUX part in whole AFE???

              Thanks...

  • 0
    TI__Mastermind 43915 points

    Hi Talha,

    The digital filter low pass characteristic repeats, or aliases back, at multiples of the modulator rate of fclk/2. Thinking of this from a purely DC perspective, if you take a FFT of the DC input signal, you will see that signal alias at roughly 8MHz and 16MHz. Take a look at Figure 44 and the text shown on page 20 describing aliasing effects in the converter. In designs, we recommend a simple first order input RC filter to knock down the aliasing signal effects. You can see on page 45 we show a recommended setup using two OPA365 drive amplifiers in combination with a 47 ohm and 2.2nF differential RC filter. You will notice that the ADS1258 does not include a internal driving buffer and for that reason, we recommend the driving op amps in combination with the low pass filter to help with aliasing effects. I am not exactly sure why you would need a high pass filter.

    Regards,

    Tony Calabria