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AM3354: Absolute maximum ratings for ADC inputs

RandyP
Guru* 84110 points
Part Number: AM3354
Other Parts Discussed in Thread: TPS65218

In the datasheet SPRS717j in the Absolute Maximum Ratings table on page 80, there is a single line for all IO pins near the bottom of the table. "Steady state max voltage at all IO pins" could in fact apply to all digital IO pins, with another unstated Absolute Maximum for the ADC inputs since they are analog pins that are most likely created differently.

Is there a different, hopefully higher value for the AIN7-0 pins relative to their supply rails or VREFN/P?

Regards,
RandyP

  • 0
    TI__Guru 55425 points

    This parameter also applies to the ADC inputs.

    Why did you assume this parameter only applies to digital I/Os?  There is not anything mentioned in the parameter description or associated note to indicate this parameter only applies to digital I/Os. The associated note even says it applies to all non-fail-safe I/Os. The only fail-safe terminals on this device are USB0_VBUS and USB1_VBUS.

    Regards,
    Paul

  • 0 in reply to peaves
    TI__Intellectual 1910 points

     

    In this case, the three voltages on the right will be around 28V nominal or 32V max.  These supplies will come up prior to the 1.8V supply for the ADC. 28V powers a switcher to make 3.3V/5.0V which powers the PMIC which generates the 1.8V  The PMIC is the TPS65218 and the 1.8V is generated by the LDO which has a 250 ohm discharge resistor.   Will this cause any damage to the  processor or cause power up sequencing issues?

  • 0 in reply to peaves
    TI__Guru* 84110 points
    Paul,

    A customer has a problem with the design because these AINn pins will have higher voltages during power sequencing. I was hoping for an alternate value for the AINn pins, even though the only answer from the datasheet was as you explained. Your very clear response should close the issue.

    David,

    Yes, since the voltages are outside the allowable voltage range, damage is possible with the customer's current design.

    Regards,
    RandyP
  • 0 in reply to RandyP
    TI__Guru 55425 points

    Randy,

    I'm not clear what you are asking.

    The requirement defined in this absolute maximum parameter doesn't have any exceptions. The device may be damaged if you source any potential to non-fail-safe pins while power is off.

    Regards,
    Paul

  • 0 in reply to peaves
    TI__Guru* 84110 points
    Paul,

    Sorry if I was not clear. I am not asking for anything more than your original reply. This and your confirmation above are what we needed. If an alternate value was available, that would be good. But it is not, the datasheet is clear and clarified against any doubts.

    Regards,
    RandyP