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TMS320F28335: Issues with ADC internal reference

Alejandro Torres
Prodigy 20 points
Part Number: TMS320F28335


Good day.

I'm writing this post to comment my problem. Theoreticaly, the ADC internal reference is 1,275V at ADCREFP pin, and 0.575V at ADCREFM. But, in several PCBs, I have 1.275V and 1,35V. My question is: The DSP is broken? How it's possible this voltages?

Thank you

  • 0
    TI__Guru* 81500 points

    Alejandro,

    A value of 1.35V for ADCREFM shouldn't be possible from the internal reference.  I would not expect the ADC to give an accurate conversion in this case, are you observing the ADC to have alot of error when converting as well?

    If you don't power up the ADC logic as part of the ADC Initialization, do you still observe this voltage on ADCREFM?  Given the magnitude the only explanation I could have is that there has been some damage to the ADCREFM pin and the internal ESD diode has blown through, causing a resistive short to VDDIO.  This would be rare, since the ADCREF pins are not typically driven  unless you are using external reference mode.

    Can you measure the current on the VDDA/VDDAIO supplies to see if they are within spec?

    Best,

    Matthew