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Original question:

ADS1278: ADS1278 High Resolution Mode

ADS1278: Real noise free bits?

Bert Gerrits
Prodigy 45 points
Part Number: ADS1278

Hi all,

At the moment I'm busy with measurements on the development board: ADS1278EVM.

De maximum Noise Free Bits that i can measure is: 17,2 - 17,24 bits in high resolution. (24-bits ADC)
My question: Is this the maximum what you could achieve?

Here you can see the settings:

Reducing the sample rate does nothing with noise free bits.



Kind regards,

Bert


  • 0
    TI__Guru 66176 points

    Hello Bert,

    Welcome to our forum and thank you for your post.

    Noise-free bits (NFB) is calculated as: log2(Vn_pp / FSR). In High-Resolution Mode, the typical noise spec of 5.5 uVrms (36.3 uVpp) equates to about 17.07 bits of noise-free resolution, so the results above make perfect sense. These specs are measured with the ADC inputs shorted and biased to a mid-supply common-mode. The results indicate the thermal and quantization noise of the ADC without external sources, so this is theoretically the best noise performance of the converter without any additional averaging applied to the raw data.

    For more information about ADC noise, check out our Precision Labs - ADCs: Noise presentations!

    Regards,