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ADS1198: Issues with sampling frequency precission

Marcelo Varela
Prodigy 70 points
Part Number: ADS1198


Hello,

We are having inconveniences with the samplig frequency precission.

Our actual configuration is 250 sps but after 24 Hs of sampling we had differents results in different ADS1198, in some cases we had an excess of neary 20.500 samples, and in other units we had 5000 samples missing.

We understand it might be caused because of the oscillator dispersion of the ADS1198.

We'd like to know if we can dissable the continous mode of the ADS1198 and to set the sampling frecuency with the MCU requesting the data every 4 ms. I mean we want to avoid the dispersion of the clock of ADS1198 by using the clock of the MCU only. 

Is this possible? or the only solution is to put an external oscilator to the ADS1198? since we have consumption limits.

Thank you and Regards

  • 0
    TI__Mastermind 38745 points
    Hello Marcelo,

    The oscillator does have accuracy tolerance that is noted on page 5 in the datasheet as 0.5% max at room temp and 2% from 0C-70C. The best way to collect data is by syncing your SPI transfers with the DRDY output pin on the ADS1198. This pin is designed to indicate to the host when new data are ready to ensure that the host can always collect a sample. If you need more precise data rates, you can look into using "Single Shot Mode" on the ADS1198. Let me know if you have specific questions about the DRDY pin or single shot mode.

    Brian