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MSP430F2617: ADC Voltage Input Saturation

Chris Minerva1
Prodigy 70 points
Part Number: MSP430F2617

Hello TI Community,

Per the datasheet, abs max voltage to any pin is VCC+0.3V. While I realize that saturating an ADC input will not give an accurate value, will it cause damage or long term reliability issues? For example, suppose I'm using VCC=3.0V and VREF = 1.5V with an analog input that may go as high as 3.3V. I only care about when the ADC input falls below 1.5V (the non saturating condition), so as long as my measurement is accurate in that range that's all I care about. As I said though, the input could spend a fair amount of time sitting up to 3.3V max. Not my design and I don't have any leverage to change the input divider without supporting rationale that this is a problem.

Please let me know.

Thank you,

Chris

  • 0
    TI__Mastermind 39560 points

    Hello Chris,

    In section 5.43 of the datasheet, it shows the Analog input range up to Vavcc, but as you mention, the results wont be accurate outside of the reference range.  Also, see note 1 of the absolute maximum ratings.  It is not recommended to expose the device to the absolute maximum ratings for extended periods and functional operation is not guaranteed outside of the recommended conditions.  I recommend changing the input divider to ensure that the input is not exposed to higher than Avcc.    

      

    (1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

  • 0 in reply to Eddie LaCost
    Prodigy 70 points

    Hi Eddie,

    So it sounds like the ESD diode on the pin is referenced to AVCC and not VREF. That's was essentially my question. I don't want the pin sinking current through the ESD diode when the input voltage is between VREF and AVCC. So you're saying it will not so long as I keep the input voltage <= AVCC, irrespective of VREF, correct?

    Thank you,

    Chris

  • 0 in reply to Chris Minerva1
    TI__Mastermind 39560 points

    Correct, per the datasheet specification, keep the input voltage <=AVCC, irrespective of VREF, to be within the recommended operating conditions.

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