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ADC14L020: Output code calculation

Daniel Nelson
Prodigy 10 points

Part Number: ADC14L020

Tool/software:

I am very confused by the datasheet on how to calculate nominal digital code outputs from the ADC. Table 1 and Table 2 and Figure 2 leave a lot to be desired and do not give out specific examples which is helpful but also not that helpful. Can anyone give specific examples of codes being outputted? Ex:  Vin+ set at this voltage and Vin- set at this voltage produces a code of 14'h0800.

Also do I have it right that the LSB is (2.6)/(2^14) = ~0.0001587V? I might be interpreting the data sheet wrong when it states full scale input voltage range. I assume that is 2.6V-0V.

  • 0
    TI__Expert 5660 points

    Hi Daniel,

    The full scale range is 2*Vref  centered around VCM.  Vref, as shown in the electrical table on Page 6 of the datasheet, is 0.8V to 1.2V.  From table 1, mid code is when the input is equal to VCM, max code is when the input is VCM+Vref/2 or nominally 1.5V+(1V/2) = 2V and the min code is when the input is VCM-Verf/2 or nominally 1.5V-(1V/2)=1V. 

    Under nominal voltage that gives you an LSB of 2V/2^14 = ~122uV.  The max swing you can get on the input is 2.4V as per electrical table on page 6 showing the max Vref is 1.2V.

    Regards,

    Geoff