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ADS1115: ALERT/READY PIN

Fernando Cardoso
Prodigy 10 points
Part Number: ADS1115

I didn´t find on ADS1115 datasheet the delay of ALERT pin working as traditional comparator. The question is simple: whats the delay time to ALERT pin goes low, after the sampled signal crosses the configured threshold ? The timing diagram does not show this important specification.

  • 0
    TI__Guru* 97415 points
    Fernando,


    The ALERT pin should transition immediately after the ADC conversion has completed reading the data and the data is above the threshold. However, I'm not sure if this is the exact answer that you are looking for.

    Again, the ADS1115 comparator is a digital comparator. It only tells you when the ADC has made a measurement and the ADC output code is larger than the threshold. This requires that the conversion completes before it triggers the ALERT pin. It does not work like an analog comparator, where the comparator triggers as soon as the input signal reaches the threshold.

    The ADC measurement does not have a sample and hold. If the input voltage is slowly rising and crosses the threshold in the middle of the conversion, the ADC may not detect it unless it is over the threshold for the majority of the data period. That means that it could cross the voltage equivalent of the threshold later in the data period, and the conversion from the ADC would still be under the threshold. The ALERT pin would not be triggered until the end of the conversion after.


    Joseph Wu