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TMS320F2812: How to calculate overall error per channel

Chuchen Wang
Expert 3480 points

Other Parts Discussed in Thread: TMS320F2812

Hello,

I have a customer using the TMS320F2812.  They are using the internal reference and is trying to calculate the error per channel. 

Looking at section 6.30.2 on pg 144 in the datasheet, there are four components that contribute to the error: Offset error, gain error, DNL error, and INL error.

The questions are:

1) How do I calculate the overall error per channel?

2) How accurate is the reading without applying any calibration?

Thank you,

Chuchen Wang

  • 0
    TI__Guru 60865 points

    Hi Chuchen,

    The total DC error can be calculated as the combination of gain, offset, INL, and DNL.  

    Typically these are added as room-sum-square (essentially adding the error powers, not magnitudes):

    Total error = sqrt(gain2 + offset2 + INL2 + DNL2)

    For this ADC, the error will be dominated by gain and offset error.  

    Without calibration, you can fill in the numbers directly from the datasheet into the above equation.  With calibration against an ideal source, the offset error can approach the ch-to-ch offset error specification and the gain error can approach the ch-to-channel gain error specification (both +/-8 LSB in this case).

  • 0 in reply to Devin Cottier
    TI__Expert 3480 points

    Hi Devin,

    Thank you very much for the quick response!  I'll forward this information along. 

    Best Regards,

    Chuchen