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INA827: Current shunt sensor

Sadashiva Kamath
Expert 1165 points
Part Number: INA827
Other Parts Discussed in Thread: OPA192

Hi,

I'm planning to use INA827 as shunt current sensor with Gain of 9.

  1. VM2 is output of INA827. Simulated waveform's screenshot is highlighted for non-expected results (in red color box).
  2. Same functionality is implemented using differential amplifier, OPA192. VM3 is output of differential amplifier, OPA192. This looks good

Question:

How to fix with INA827? Do you suggest any alternate solution in place of INA827?

Tina model attached

6886.currentSense2.TSC

  • 0
    TI__Genius 10850 points

    Hi Sadashiva,

    Thanks for your post, I can help you. 

    The power supply range is 30V single supply in the schematic you shared. If we put meter probes on each input of the INA, you will see that IN- changes from 0 to 23.89V. And IN+ changes from 340mV to 23.9V:

     

    At the fall of the square wave, the common mode voltage is approximately 170mV. At the top of the square wave, the common mode voltage is approximately 23.9V. This change in common mode voltage is too drastic and fast for the INA to process. I would recommend changing the input signal such that the common mode voltage remains the same and you are only changing the differential voltage. 

  • 0 in reply to Tamara M Alani
    Expert 1165 points

    Thanks for response, This helps..!

    Circuit shown is for high-side shunt current sense. Input signals are changing like the way it is simulated (I mean, change in common mode voltage is too drastic and fast). I don't have any control on input signals. 

    Question:

     Do you suggest any alternate solution in place of INA827?

  • 0 in reply to Sadashiva Kamath
    TI__Genius 10850 points

    Hi Sadashiva,

    Sorry for the delay here. You may consider a high-side current sensing approach. Please see the attached TINA file. Your circuit is on the left, My proposal is on the right. 

    INA827 Current Sense proposal.TSC