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INA290-Q1: Input Bias current into IN+ and IN-

Henrik Leegaard
Prodigy 10 points
Part Number: INA290-Q1


Tool/software:

I am planning to use INA290-Q1 /A1 Device) as current sensor

In some cases there will be 40V at IN+ and IN-, but no voltage at Vs, the voltage difference between IN+ and IN- (Vsense across sense resistor) will be 0V

If I look at figure 6-15 in the data sheet, I would have assumed the input bias current into IN+ and In- would be close to 0uA

But in Spice simulation and in real life, the bias current into IN+ and In- is approx. 39uA each

Please clarify how I miss read the datasheet

  • 0
    TI__Expert 5765 points

    Hi Henrik,

    To confirm: there is a VCM of 40V, but there is no current flowing through the sense resistor? Can you please share a schematic of your board or image of your Spice model?

    You are correct, if the supply is 0V and the Vsense is 0V then there should be an IB ~0uA.

    I would recommend you run a test (or share the scope shot if you already did this):

    Step Vs from 0V-5V and monitor the Vsense, IB, and Vs. Then step the supply back down to 0V (5V-0V) and monitor the same voltages and currents. 

    Best,

    Holly

  • 0 in reply to Holly R
    Prodigy 10 points

    Hi Holly

    I have attached the Spice simulation schematic and test result.
    As you can see the IN+ and IN- input current is not 0uA but approx. 19uA

    BATT+ is steady 32V

    VS is steppe from 0 to 5V

    In my last simulation I must have done something different to get 39uA

    Regards

    Henrik

  • 0 in reply to Henrik Leegaard
    TI__Expert 5765 points

    Hi Henrik,

    This looks like a limitation of our spice model.

    Do you have any results from your real life test that you can share? I would like to see the same measurements: VS, IB, and Vsense.

    Best,

    Holly

  • 0 in reply to Holly R
    Prodigy 10 points

    Hi Holly

    I don't have any stable real life measurements yet

    I need to make a new PCB in order to do the measurements

    Regards

    Henrik

  • 0 in reply to Henrik Leegaard
    TI__Expert 5765 points

    Hi Henrik,

    Ok. If the issue exists on a physical board please let me know.

    Best,

    Holly