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AM2634-Q1: Question of internal ADC_VREFHI

Phoenix Yin
Prodigy 130 points
Part Number: AM2634-Q1
Other Parts Discussed in Thread: AM2634

Hi,

In AM2634 RM (SPRUJ17E – MARCH 2022), page 452, like red lines 

From here, it saying the measured ADC input range is 0 - 1.8V.

But on the next page, it showing:

Clearly, it could measure 0 - 3.3V.

Questions:

1. By using internal VREFHI = 1.8V, VREFLO = 0V, could we measure up to 3.3V?

2. In my application, should I use 4096 or 4224?

Thanks

  • +1
    Prodigy 130 points

    I have figured out that when using 1.8V internal vrefhi, the measured voltage should be 1.8 * 32/18 = 3.2V, but it is only on datasheet, not in TRM?

    So the ADC calculation should be adcCount/4096 * 3.2V or adcCount/4224 * 3.3V as second picture shows.

    In this case, I think the fomular in the first picture is NOT CORRECT. It should be AdcIn = VREFHI * 32/18 * (AdcCount/4096), VREFLO = 0.

  • 0
    TI__Genius 15762 points

    Hello Phoenix,

    1) Yes, the design enables the ADC to read up to 3.3V signals with only a 1.8V reference.

    2) I am not sure I understand your question, are you asking what numbers you should use for the calculation?

    -4095 will be the maximum value reflected in the ADC Results Register.

    Best Regards,

    Zackary Fleenor