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ADC reference register

Bruce Zheng
Prodigy 130 points

Other Parts Discussed in Thread: CONTROLSUITE

Hi GUYs!

I have a problem related to the ADC settings. I try to sample the voltage value of the 3V3SNS power suppy on board using the ADC.

But there is a constant difference between the real voltage value and the value got by the ADC.  I can't figure out why. The resolution of the ACD

is set to be 12-bit. So I calculate the voltage using equation Voltage=AdcbResultRegs.ADCRESULT0*4095/3.3,    

By the way, I also want to figure out what is ADCPPB4OFFREF Register used for. At first, I thought this register is an offset for the result register and by changing the value of this register can my previous problem be solved. Then I tried my thought in the program. But nothing changed.

Thank you for any advice and ideas.

  • 0
    TI__Guru**** 480451 points
    Hello,
    I will move your question to the relevant device forum. The experts there can help you best.

    Thanks
    ki
  • 0 in reply to Ki
    TI__Guru 60865 points

    Hi Bruce,

    ADCs don't have perfect accuracy, so the first step would be to check the gain, offset, and linearity specifications in the device datasheet to see if the variance you are seeing can be explained by the expected inaccuracy inherent in the ADC.

    As far as the PPB, this can be used to compensate for an external offset on a given channel.  You first have to point the PPB to the given SOC you are using to sample that channel.  You can read about the PPB in the device TRM, and you can also look at the ADC PPB examples in ControlSUITE.