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MSP430FR5969: ADC input damage/anomalous behavior levels

Erwin Vigilia
Prodigy 10 points
Part Number: MSP430FR5969


Tool/software:

MSP430FR5969 ADC input in my application can hit -0.4V for a few milliseconds, would this voltage cause damage or cause the micro to behave incorrectly after the voltage returns to normal? (0-2.5VDC)

  • 0
    TI__Guru 71216 points

    Hi Erwin,

    Generally no, but the spec in the datasheet shows -0.3v and current in/out of any pin can be up to 2.0mA.  So what is connected to the ADC input that drives the pin below VSS?

  • 0 in reply to Dennis Lehman
    Prodigy 10 points

    It's connected to the output of an opamp through a series ~5k resistor, with a Schottky in parallel with the input to the ADC. The sequencing of the supply rails, -5V first, +5V second, causes the output of the opamp to become negative until the +5V comes up as much as ~500mS later. The resistor should limit the current to just under 1mA. We have not experienced any issues - this was brought up during a design review as an action item to clear with TI. Older ADCs had issues with negative inputs, so I understand why this was brought up.

  • 0 in reply to Erwin Vigilia
    TI__Guru 71216 points

    Hi Erwin,

    Based on my experience and the fact there is a series limiting resistor keeping the input current below -2mA, you should be good to go with this design.

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