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TMS320F280049: ADC Offset Calibration w/ VREFLO Sampling

Ricky Zhang
Genius 9520 points
Part Number: TMS320F280049


Hi, Champs,

I noticed that we have ADC VREFLO sampling on Soprano with channel 8 and 9, but there's no block diagram shows this on Potenza DS/TRM, however, it seems we documented in DS/TRM on the analog pins and internal connections table that channels 13 will be connected to VREFLO.

So my question is, do we simply configure ADCSOC channel select to 13, then we can sample Vreflo, without any further configuration like Piccolo B does to enable Vreflo bit in ADCCTL1 register?

My customer would like to sample it periodically and do offset calibration across full range temperature to improve ADC accuracy, do you think it works or if you have any other better options?

Best Regards,

Ricky Zhang

  • 0
    TI__Guru 60865 points

    Hi Ricky,

    Yes, you can just setup the SOC channel select to point directly to the desired internal channel, and then sample; no additional muxing required.  This is because each of the 3 or 4 ADCs on F28004x or F2837x devices has 16 channels vs earlier devices like F2803x which had only 16 total channels (so we needed an additional level of muxing to fit everything).  

    The offset error is already pretty good on these devices; you won't see much improvement from continuous self-calibration (but you definitely can do this, if desired). 

    There was a pretty thorough discussion of self-calibration, external calibration, and overall ADC accuracy in this thread:

  • 0 in reply to Devin Cottier
    TI__Genius 9520 points

    Devin,

    Thanks for your confirmation and additional information.

    If customer wants to get high accuracy for ADC across full temp range, what's your suggestions to guarantee this except for offset calibration?

    Best Regards,

    Ricky Zhang

  • 0 in reply to Ricky Zhang
    TI__Guru 60865 points
    Hi Ricky,

    (1) It is worth noting that the accuracy is very much improved vs. previous devices; the datasheet min/max specifications do include temperature and voltage drift already.

    (2) Per the linked thread, you can maybe squeeze out a little more accuracy by doing external gain calibration. Whether you do external gain calibration or not, you will want to use an accurate external reference if accuracy is really important.
  • 0 in reply to Devin Cottier
    TI__Genius 9520 points

    Devin,

    Okay, thanks for your further information.

    I'd communicate with customer on this.

    Best Regards,

    Ricky Zhang