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ADS1115: Actual/Total Noise

Part Number: ADS1115

Hi Team,

Need your inputs on this. Our customer has a question regarding the noise characteristics of ADS1115. Figure 19 of its datasheet shows the total error as +/- 4 µV whereas Table 1 shows RMS noise of 62.5 µV (which oddly seems to just be the LSB of the configuration) at +/- 2.048 FSR. We just need clarifications on how these two relate to the actual/total noise. We are specifically interested in the noise on the 0.256 FSR.

Thanks in advance.

Kind Regards,

Jejomar

  • Jejomar,


    In the ADS1115, the noise is smaller than the LSB in most configurations. That's certainly the case when comparing the LSB with the RMS noise. In tables 1 and 2, where we list the noise performance, we have listed the LSB voltage when the noise is smaller than the LSB.

    Looking at Figure 19, that looks like an error to me. I believe that should read "mV" instead of "uV". Most of this error comes from gain error. The max gain error is listed as ±0.15%, and that error on the ±2.048V is just over 3mV. Noise and offset added the error is still dominated by gain error. I'll make a note of this and we'll change it when we revise the datasheet.

    For the noise in the ±0.256 FSR setting, I would still use Figure 1 and look that the noise free values. That gets the peak to peak noise for the operation at data rates of 128SPS or higher.


    Joseph Wu