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INA200 OUTPUT ERROR

imtiaz khan
Intellectual 440 points
Other Parts Discussed in Thread: INA200, INA282

Dear All

Using two INA200 to sense current in HIGH and LOW side of a load. The system power supply is 28VDC. Current sense resistors are 0.01 Ohm each. Sensed current is 550mA. Filter resistors are 100 Ohms each in series with inverting and non-inverting inputs.

Given the the published characteristics the calculated ideal voltage output as measured at pin 2 of INA200 should be 20*0.55*0.01 = 0.11 volt. The actual measured voltages, however, are:

                     for the high side = 0.0961 volt

                    for the low side = 0.1086 volt

Note that high side INA200 is measuring in the presence of 28 VDC common mode voltage whereas low side INA200 is within few millivolts of ground common mode voltage.

Given the above scenario can anybody shed some light on the measured output errors as given above, particularly the high side one.

 

Regards

i.k.

  • 0
    TI__Mastermind 25805 points

    Hello imtiaz khan,

     

    Using a 10mohm sense resistor with an expected load current of 550mA would yield a Vsense of 5.5mV. 

     

    This falls into one of the “Low Vsense” cases which are outlined on pages 10-11 of the PDS.  These cases are not designed for accurate operation.  Given that your Vcm is 28V and your Vs must be less than 18V, you are actually in Low Vsense Case 3.

     

    One other observation is that the INA200 is not recommended for low-side current sensing

     

    You may want to consider the INA282 with an external comparator.  Drawbacks include lower bandwidth and the need for an external comparator.  But, the device has only 70uV of offset and can be used for both low and high-side current sensing.

  • 0 in reply to Pete%20Semig
    Intellectual 440 points

    Hello Pete

    Thanks for the insight.

    Regards

    i.k.