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Questions about ENOB (AC Metric) and effective Resolution ( DC Metric) from Precision Lab ADC

Yan Fan
Intellectual 360 points

Dear Ti Precision Lab Staff, 

Thank you very much for putting together the Precision lab ADC. 

I have one question after watching the video: We basically used the input-referred noise and effective resolution ( DC FOM) to determine what is the bit / gain required for ADC based on specific application. But I did not see that AC FOMs such as ENOB was used for such purpose, at least from the lecture. Whether the ENOB is a way to judge the noise level of ADC rather than a metric to determine bit / gain required for a specific ADC? 

Thank you in advanced, 

  • 0
    TI__Mastermind 46231 points

    Hi Yan,

    Input-referred noise is a measure of noise, as its name implies. This applies for both AC and DC signals.

    ENOB (whether AC or DC, though "DC ENOB" should be referred to as effective resolution) is a figure of merit to help you determine how many bits are required for a specific application. ENOB, whether derived from SNR or SINAD, is a measure of an application's or ADC's dynamic range, and therefore depends on the input-referred noise.

    Let me know if this makes more sense.

    -Bryan

  • +1 in reply to Bryan Lizon86
    Intellectual 360 points

    Hi Bryan, 

    Thank you very much for your response. My confusion was not what are these metrics but, which is the dominant factor between the ENOB DC or ENOB AC? is that related to whether our application is focused on low frequency vs high frequency? 

    Thank you in advance

  • 0 in reply to Yan Fan
    TI__Mastermind 46231 points

    Hi Yan,

    Again, I will reiterate that "ENOB DC" is an incorrect term and should instead be referred to as effective resolution.

    ENOB is purely an AC characteristic and is used to parameterize systems that measures AC signals.

    Effective resolution is generally used to parameterize a system that measures DC signals.

    If this does not answer your question, please help me understand what else you would like to know.

    -Bryan