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Original question:

MSPM0G3107: ADC Configuration

MSPM0G3107: ADC value fluctuating in MSPM0G3107

Paul K Joy
Prodigy 150 points

Part Number: MSPM0G3107

Hi,

I am using MSPM0G3107 for my project.
In my board, An external circuitary is used to convert phase to 12V DC which is further divided to provide stable 3.3V to the MCU.
I am using ADC0 , channel 11 for reading Temperature.The reference taken is VDDA.
When I am trying to read the temperature ,the  ADC value is fluctuating.
When the external circuit is removed and MCU is powered via launchpad, the temperature reading is correct and stable.
What could be the potential reasons for this?

  • +1
    TI__Expert 7135 points

    There could be noise on your supply line, especially using any type of switching buck regulator. The LP takes the 5V input and drops it down with an LDO which is not a switching supply, so you will see more stability there. You could try to do some frequency analysis to see where the peak frequency magnitudes are on the VDD line and use a filter to remove/mitigate the noise. 

    Since the VREF for the ADC is VDD, any noise/transients on the supply will translate to the ADC as well, potentially throwing off the value quite significantly.