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AM2634-Q1: How to do ADC calibration for AM2634?

Phoenix Yin
Intellectual 295 points
Part Number: AM2634-Q1
Other Parts Discussed in Thread: AM2634

Hi,

I have read this thread about calibration, https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/1136134/am2634-q1-am263x-adc-calibration-question

It seems the trim data still not avaialbe on the mcu, I cannot see any value in ADC ADCINLTRIM1-6, they are all 0.

In this case, how could we calibrate ADC? 

In the latest TRM, the ADC calibration section was removed. Could you please point out where can I find this information for AM2634?

Thanks

  • 0
    TI__Guru*** 135355 points

    Hello Phoenix,

    The section was removed as it contained information that was not actually applicable to the AM2634 device as we don't store any data in the ADC trim registers.

    Phoenix Yin said:
    In this case, how could we calibrate ADC? 

    My understanding is that the ADC_CAL0 and ADC_CAL1 pins would be used for calibration, but let me loop in another expert to further comment on this.

    Best Regards,

    Ralph Jacobi

  • 0 in reply to Ralph Jacobi
    Intellectual 295 points

    Hi Ralph,

    Thanks for your reply.

    And yes, I am looking for the ADC calibration procedure with CAL0 and CAL1, please explain more on it.

  • 0 in reply to Phoenix Yin
    TI__Mastermind 23013 points

    Hello Phoenix,

    We are looking into your question now and will provide you with some feedback within the next two days.

    Thank you,

    Best Regards,

    Zackary Fleenor

  • 0 in reply to Fleenor
    Intellectual 295 points

    Hi Zackary,

    Any feedback available now?

  • 0 in reply to Phoenix Yin
    TI__Mastermind 23013 points

    Hello Phoenix,

    Apologies for delay here. Providing initial feedback below. We plan on creating an App Note to better describe this process.

    Sri Gunturi's answer on this reference thread summarizes the same idea: https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/1136134/am2634-q1-am263x-adc-calibration-question

    The intention is to use the ADC_CALx pins for this purpose. They are a common input to all ADC, so you can use them to remove/calibrate for ADC to ADC differences across the device and calibrate all ADC to an external source signal.

    1) Take measurements from a dynamic/static signal source

    2) Measure a precision system reference using the ADC_CAL pins

    3) Remove all DC error from the system,

    4) Calibrate the gain from each ADC,

    5) Re-take the measurement of the dynamic/static signal source and compare how much closer each ADC is to each other and the reference signal after cal. Do the same showing how temperature changes would affect that and how you could do a periodic cal that accounts for changes during runtime...etc.

    Alternatively, if the ADC_CALx pins did not exist, then you would need to route a common signal on the PCB to each ADC and then sacrifice an input channel to give you this calibration feature. 

    If you need maximum performance, then in-system, runtime calibration should not rely on those defaults. But instead, just measure what the current performance is. This will change as a function of operating voltage, temperature and process aging over time. 

    Best Regards,

    Zackary Fleenor