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Original question:

ADS41B29: ADS41B29

ADS41B29: Question about SNR

Gabriel Wang1
Genius 4575 points
Part Number: ADS41B29
Other Parts Discussed in Thread: ADS4129, ADS5463

Dear Expert

There is a curve in the specification that I didn't understand: the relationship between input voltage and SNR. Why does the larger the input amplitude, the lower the SNR trend? Shouldn't the larger the input signal, the larger the SNR?

But I see the ADS4129's SNR is going high .

  • 0
    TI__Mastermind 33610 points

    Hi Gabriel,

    It could be true, the higher the analog input signal level the more stress you put on the ADC, which could resolve itself as a lower SNR measurement.

    Otherwise, I believe the ADS129 datasheet might be in error here. We would have to check.

    Let us know if you would like us to do so on the lab bench.

    Regards,

    Rob

  • 0 in reply to Rob Reeder
    Genius 4575 points
    Rob Reeder said:

    Dear Rob

    I don't think it's right. I think 4129 is right. SNR is the logarithm of the ratio of signal to noise, and noise generally does not change. However, the signal is variable. In theory, the lower the signal amplitude, the smaller the SNR, the higher the signal amplitude, and the larger the SNR. The corresponding curve between SNR and signal amplitude in ADS5463, a 500M frequency ADC, is also the same as 4129. I think this is correct.
  • 0 in reply to Gabriel Wang1
    TI__Mastermind 33610 points

    Hi Gabriel,

    I agree, the ADS4129 figure is correct, this figure is in error, SNR should be referenced in dBc not dBFS.

    Regards,

    Rob