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ADS1263: Internal clock accuracy impact on 50/60 Hz rejection.

Tony Merolla
Prodigy 120 points

Part Number: ADS1263
Other Parts Discussed in Thread: ADS1262

The internal clock of the ADS1263 is specified at ± 2%.  When using the digital filters for 50/60 Hz rejection does this this frequency tolerance reduce the capability to reject those frequencies?

Thank you.

  • 0
    TI__Mastermind 44760 points

    Hi Tony,

    Yes, the internal oscillator's frequency tolerance will have an impact on the 50/60 Hz rejection... The ADC's data rate scales proportionally with the clock frequency; and therefore, the filter notches will also scale proportionally.

    ...You can observe this effect in the ADS1262's Excel Calculator Tool (http://www.ti.com/tool/ads126x-calc-tool) by modifying the clock frequency and zooming in on the filter response around 50 and 60 Hz.

    You can lessen this impact by using the higher-order SINC filters (SINC2/3/4), as the higher order filters have wider notches. Otherwise, to improve the tolerance of the clock frequency you'd need to use an external crystal or crystal oscillator to provide the ADC clock.

    Best regards,
    Chris