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ADS1255 with 8.0MHz input clock from GPS

Paolo Gerini
Prodigy 40 points
Other Parts Discussed in Thread: ADS1255, ADS1282

Hello,

I'm developing AD conversion board for seismic applications based on ADS1255. Since I have to synchronize different boads, I will use an input clock coming from a GPS receiver. Unfortunatly my GPS isn't able to provide a 7.68MHz clock but only 8.0MHz. Is there any way to get the data rates described into the datasheet with an 8.0MHz input clock?

Best Regards,

Paolo Gerini

  • 0
    TI__Mastermind 44550 points

    Hi Paolo,

    Scaling the ADC clock will inevitably scale the ADC data rates, all data rates would increase by a factor of:

    8MHz / 7.68MHz = 1.0416666... (i.e. 1000 SPS becomes 1041.6666... SPS)

    The 8MHz clock is not a problem for the ADS1255; however, the SINC filter notches (which occur at multiples of the data rate) will shift and would not provide as much 50/60Hz rejection (for example), as they would for a 7.68 MHz clock.

    Other options would be to:

    • Re-clock the GPS clock
    • Perform additional signal processing on the ADC data if you want to have a different filter response.
    • Use a different ADC with an FIR filter (such as the ADS1282), instead of a SINC filter.

    What data are you trying to achieve?

    Best Regards,
    Chris