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INA219: INA219 bias current error

Wayne Wang20
Expert 4370 points
Part Number: INA219

Hi team,

My customer is testing INA219.  During test, we found a error always exists there. The test condition is that we disconnect the load from supply and use Digital multimeter to measure the voltage across Rshunt and 0.1uF cap. The Rshunt voltage is 0.21mV but the 0.1uF cap voltage is 0.8mV. This means there is a error added by the Rfilter. What's more, we also found that reduce the Rfilter value will reduce this error. So I am thinking if this error is due to INA219 IN+ bias current and IN- bias current is not balanced?

So could you please help give some advice on what is the root cause? And how should we get rid of this error? Can we just reduce Rfilter to 0 ohm? Thanks.

regards,

Wayne

  • 0
    TI__Intellectual 1235 points

    Hi Wayne,

    The input filter is suggested only if you expect a noisy input. If noise is not an issue, you can simply remove the input filter and avoid the error it introduces. 

    If there is noise on the input that needs to be filtered out, you can help reduce this error by decreasing the Rfilter values as you observed. The error can also be decreased by precisely matching each Rfilter resistor as close as possible. 

    Here a TIPL training video that discusses how to analyze and calculate input filter error here. 

    Thanks,

    Cierra

  • 0
    Guru 140200 points

    Hi Wayne,

    keep in mind that the INA219 has an additional internal 320k resistor from the VIN- pin to ground.

    Kai