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MSPM0G3519: MSPM0G3519: ADC conversion result different for ADC0 and ADC1

Khanh Doan
Intellectual 330 points

Part Number: MSPM0G3519

Hi TI team,

I have one question regarding ADC conversion for ADC0 and ADC1 (with voltage reference is VSS, 10 bit resolution).

Currently, I'm doing an experiment that when I measure ADC on A0_4 without voltage, the value is small around 18-20 . This is correct and the result also fine when I apply voltage with value range from 0 - 3. Then I try to do the same on A1_4. When there is no voltage, the result is large 357-402 (around 1.15 - 1.29V). When there is voltage around 3V apply to the pin, the result is incorrect also. Do you have any hint about this issue ? 

  • 0
    Guru 43955 points

    Is this on a launchpad?

    Is there anything else on the pin?

    What do you mean by "incorrect"?

  • 0 in reply to Keith Barkley
    Intellectual 330 points

    1/ Yes, this is on the launchpad MSPM0G3519. 
    2/ No, there is nothing else on the pin. I just make a measurement on the 2 different unit ADC0 and ADC1. The behavior described above. And when I apply voltage to pin for ADC1, it seems to be in correct. For example, if I apply a 3V to pin A0_4 (VDD is 3.3V, resolution is 10 bit) => Then the result is 930-940, which is correct. But then when I try with the A1_4 , it is 340-400. I think this is incorrect. 

  • +1 in reply to Khanh Doan
    TI__Expert 7790 points

    Hi Khanh,

    I am seeing the same readings of 930-940 on both A0_4 and A1_4. Are you able to share your application code and device configuration settings?

    Best Regards,
    Brian

  • 0 in reply to Brian Lee
    Intellectual 330 points

    Hi Brian,

    I checked again and it works fine for all channels. I notice the incorrect behavior only when I keep the analog pin floating. It seems to be that the ADC value read from unit 0 when the pin is floating is in smaller range (0-100). While the ADC read from unit 1 when the pin is floating is in range (200-400). 

    Thank you so much for your support