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MSP430FR2433: Open-Drain I/O Configuration

W_ilson
Intellectual 1820 points
Part Number: MSP430FR2433


Hi Team,

Is there any way to implement an open-drain I/O on the MSP?

Is it as simple as toggling between Hi-Z and Output Low?

Best Regards,

Michael

  • 0
    Guru 100785 points
    Yes, input-with-pullup vs output-low is as close as it gets. I think the main difference from True open-drain is that you aren't allowed to pull up above VCC.
  • 0 in reply to Bruce McKenney
    TI__Intellectual 1820 points
    Hi Bruce and Team,

    Thanks for the insight.

    Are there any other downsides to this type of configuration? Also, if this is implemented if firmware, is it recommended to use the internal or external pull up?
  • 0 in reply to W_ilson
    TI__Genius 14775 points
    Wilson,

    This E2E post ( e2e.ti.com/.../18698 ) has some additional information on the trade-offs between an external and internal pull-up resistor if you read through it. It all depends on the customer's priorities and whether they want to prioritize mitigating leakage current (using an external pull-up resistor) or if they want to prioritize area and cost (using internal pull-up resistor). Both will be able to accomplish the task at hand.

    Best regards,

    Matt Calvo
  • 0 in reply to W_ilson
    Guru 100785 points
    The internal pullups are rather weak (30k-50k), so you probably don't want to use them for a fast bus (or noisy environment). Many years ago I tried using internal pullups for an I2C; my wires were very short and I ran the bus pretty slow, but even so it was quite fragile.

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