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INA220 / Unexpected voltage on Vin- and Vin+ pin

S.Satoshi
Guru 21675 points
Other Parts Discussed in Thread: INA220EVM, INA220

Hi Everyone,

Now our customer has evaluated INA220 as inserted circuit and then they has confirmed the behavior when Rsns and ferrite beads will be opened and DC/DC will be off. We tried to confirm this behavior by using INA220EVM, then we confirmed unexpected voltage on Vin- pin and Vin+ pin. This voltage looks like flowing from Vin+ pin or Vs pin. Can you explain why the voltage flow from Vin+ or Vs pin to Vin- pin? And can we prevent this behavior?

Best Regards,

Sonoki / Japan Disty

  • 0
    TI__Genius 14825 points

    Sonoki,

    Thank you for your question, I will look into it and let you know.

    Jason Bridgmon

  • 0 in reply to Jason Bridgmon
    TI__Genius 14825 points

    Sonoki,

    Internally, between VIN+ and VIN-, there is a resistance of a few kOhm.  If you drive one pin and float the other, then you will see a similar voltage present on the open pin.

    Also, there are switches between the power and the inputs, so if both inputs are floating, there is a current path that will make the inputs have some potential on them.  It is difficult to trace this path through the design so we cannot give you an exact voltage that it will float to, or even be able to say if it is consistent.


    There is no internal way to stop this; the device wasn't designed to operate with open inputs.  It may be possible to use clamping diodes or pull-down resistors or something of that nature, but I don't know how much those will impact the operation and accuracy of the circuit and will only limit the floating potential and not eliminate it.

    If there are any other questions you have, I'm happy to answer them.

    Regards,

    Jason Bridgmon

  • 0 in reply to Jason Bridgmon
    Guru 21675 points

    Hi Jason-san,

    Thank you for your response. I believe that these information will be enough so far, so I verified your post for now. Please let me ask when I receive additional question from our customer.

    Best Regards,

    Sonoki