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INA240A1 Offset Current

nphansen
Prodigy 70 points
Other Parts Discussed in Thread: INA240

I'm considering using the INA240A1 for high side current measurement.

I would like to add a filter on the input as described in the datasheet. I'm aware of the expected gain error. This is acceptable since I do not need accurate gain. However, Im concerned about offset error. Only the typical bias current is specified, offset current is not specified.

How well does IB+ and IB- match? What kind of offset error kan be expected for a given filter resistance?

Thank you

  • 0
    TI__Genius 15760 points
    Hi nphansen,

    Copying Guang, apps engineer of INA240, for support.

    Regards,
    Mayrim
  • 0 in reply to Mayrim Verdejo
    TI__Mastermind 34900 points

    Hi nphansen,

     

    The bias current tracks really well, only when the differential input voltage is 0. However this is not a very useful situation. That is why figure 32 is attached in the data sheet to show the divergence of IB. This is the reason why any line resistance should be kept to minimal.

    Regards,

    Guang-Apps CS Products

  • 0 in reply to Guang Zhou
    Prodigy 70 points

    Thank you for your response. However, it doesn't really help me. The datasheet only describes a gain error which is within what I can accept. However, I'm concerned about low current measurement so I would like to have data for the expected offset.

    Do you have any data for the input offset current? Considering the magnitude of the bias (90 uA), even a small difference can cause a large offset error. In order to set an upper limit on my series resistors I need to know the maximum offset current.

  • 0 in reply to nphansen
    TI__Mastermind 34900 points
    Hi,

    3uA max, under the condition of 5V supply, 2.5V output reference and 12V common mode input, at room temperature.

    Regards
    Guang