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TM4C123GH6PM: Question on using ADC

Keith Smith
Intellectual 330 points
Part Number: TM4C123GH6PM


I have questions on using the ADC on the TM4C.

I have an external circuit supplying the voltage to the ADC.

I have multiple boards running the same firmware, but the ADC values do not agree with the same voltage input.

I have noticed that there is a slight variation in VDDA from board to board.

How accurate is VDDA expected to be?

If VDDA is accurate to V3.300, how much variation is expected in the ADC input? Meaning what is expected variation of the ADC itself.

How much changed in ADC input is seen with a 0.1% change in VDDA?

  • 0
    Guru 27665 points

    e2e.ti.com/.../Bookshelf

    Keith Smith said:

    I have multiple boards running the same firmware, but the ADC values do not agree with the same voltage input.

    I have noticed that there is a slight variation in VDDA from board to board.

    Hardly surprising, do they vary from the specifications?

    Keith Smith said:
    How accurate is VDDA expected to be?

    It isn't. It's an input to the micro not an output. There are requirements on the input range. However keep in mind that VDDA is your reference.

    Keith Smith said:
    If VDDA is accurate to V3.300, how much variation is expected in the ADC input? Meaning what is expected variation of the ADC itself.

    RTFM. Once you have then ask questions about what you do not understand in the manual.

    Keith Smith said:
    How much changed in ADC input is seen with a 0.1% change in VDDA?

    See the answer to your first question.

    Robert