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ADS1115 Settling Time and Impulse Response

NAOKI AOYAMA
Guru 11215 points

Other Parts Discussed in Thread: ADS1115

Hello,

My customer uses the ADS1115 for measuring four signals.

He wants to get data with high accuracy, so he wants to know the settling error and

impulse response when switching the channel on a internal multiplexer.

Do you have the characteristics of settling time and impulse response?

Regards,

Naoki Aoyama

  • 0
    TI__Guru** 101005 points
    Naoki-san,


    The ADS1115 digital filter settles in one cycle, so each conversion result is valid if the input is fully settled. This is important for single-shot mode of operation.

    This digital filter is basically a sinc filter in the frequency domain, so it becomes linear averaging in the time domain.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Guru 11215 points
    Hi Joseph-san,
    Thank you for your fast reply.
    I understood it is important the input signal is fully settled.
    For the input is fully settled, I think it is necessary the input source has a low impedance.
    Do you have a guideline of the impedance value?
    The customer uses the ADS1115 with setting FS=0.256V and 4.096V.

    Regards,

    Naoki Aoyama
  • 0 in reply to NAOKI AOYAMA
    TI__Guru** 101005 points
    Naoki-san,


    Generally, I think the input filter resistors should be 1kOhm or less. Larger resistors than this may affect the linearity of the ADC measurement near 0V.

    Note that the filter resistors may affect the settling of the input sampling capacitors. However this is not what we are talking about when we refer to single cycle settling. Single cycle settling refers to the effect of the digital filter. Some ADCs have higher order digital filters that require several samples to settle.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Guru 11215 points
    Hi Joseph-san,

    Thank you for your very fast reply.
    I refer to your information. I will feedback to the customer.
    Thanks,

    Naoki Aoyama