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TMS320F28384S: The ADC performance.

Luke Chen
Expert 5090 points
Part Number: TMS320F28384S


Hi champs,

If we want to compare the performance ADC, I have below two questions need your comments,

  • Should we check the ENOB of AC Characteristics or the parameters(Gain Error, Offset Error, etc.) of DC Characteristics?
  • Can we convert the ENOB to error in LSB?

Thanks and regards,

Luke

  • 0
    TI__Guru 60865 points

    Hi Luke,

    Which specifications are important is going to be highly application / implementation dependent.  

    ENOB is a measure of noise and distortion performance, so this will affect the precision.

    ENOB is directly proportional to SINAD (specified in dB) so you could certainly convert the SINAD value in dB to voltage or LSBs.  

    Gain, offset, and linearity are the main contributors to absolute accuracy, so you'd want to look at these if accuracy is important. 

    Furthermore, gain and offset errors are very systematic, so one or both may be tolerable to the application.  It may also be able to calibrate out some of the gain and/or offset error in the final system.  Linearity error,  on the other hand, is probably not something you can do much to work around.  

  • 0 in reply to Devin Cottier
    TI__Expert 5090 points

    Devin,

    According to datasheet, we say the ENOB is 11.2 bits of single-ended 12-bit ADC.

    My customer wants to know how many LSBs does it mean, how should I respond him please?

    Regards,

    Luke

  • +1 in reply to Luke Chen
    TI__Guru 60865 points

    Hi Luke,

    ENOB is a measure of noise and distortion performance.  It is directly related to SINAD (signal to noise and distortion ratio) which is measured in dB.  So 11.2bits of ENOB = 1.76 + 6.02*11.2 = 69dB of SINAD.  69dB of SINAD means that a full-scale input signal, after being resolved by the ADC, would be (69/20)^10 = 2818 times as large as the noise + distortion.  

    Note that ENOB only measures the noise + distortion performance.  Accuracy (which would be more likely to be measured in LSBs, Volts, or mV) is comprised of gain, offset, and linearity (INL/DNL) errors and is mostly independent from the ENOB (an ADC could be very accurate, but have poor ENOB, or could have very good ENOB, but not be very accurate).  

    You might want to refer the customer to the TI precision labs videos that explain ADC specifications here: https://training.ti.com/introduction-analog-digital-converters-adcs