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F28E120SC: F28P550 100PIN: Can we use VREFHI and VREFLO as 4 ADC input at the same time When use VDDA as reference?

Zane Wei
Intellectual 1965 points

Part Number: F28E120SC
Other Parts Discussed in Thread: LAUNCHXL-F28P55X

Hi Team,

I can't find P55 part number, so use E12 ask question for P55. Can we use VREFHI and VREFLO as 4 ADC input at the same time When use VDDA as reference?

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  • 0
    TI__Genius 9260 points

    Hello Zane,

    Apologies for the late reply! Many team members are out of the office this time of year.

    On F28P55x, when the ADC reference is configured to VDDA/VSSA, the VREFHI and VREFLO pins can be repurposed as additional ADC input pins. However, in VDDA/VSSA reference mode there is a resistive connection between VREFHI and VREFLO when they are used as analog inputs. Because of this, we recommend driving only one of the two pins and leaving the other floating. So you should not use VREFHI and VREFLO simultaneously as independent ADC inputs and therefore you cannot treat the 2*VREFHI + 2*VREFLO pins as 4 independent ADC inputs at the same time.

    Also, on the LAUNCHXL-F28P55x hardware, the two VREFHI pins are shorted together and same for VREFLO, reinforcing that these pins are intended to be one reference node rather than multiple independent analog inputs.

    Best Regards,

    Masoud