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INA225-Q1 Accuracy of gain error at low Vout

Tomoaki Yoshida
Expert 2200 points
Other Parts Discussed in Thread: INA225-Q1, INA300, INA225, TIDA-00328

Hi

 

I'm considering the current sense system very wide range.

The range is about 100A from 0A.

So, I'm looking for a current shunt monitor can also be output at low input.

I think that INA225-Q1 is good, but gain error of electric charactoristics are listed in the range of Vout is between 0.5V and Vs-0.5.

I want to know gain error and INL around 0V.

Are there data of gain error and INL around Vout is 0V.

 

Best regards,

Tomoaki yoshida

 

  • 0
    TI__Intellectual 2480 points

    Hello Tomoaki,


    What is your desired output range?  Are you seeking a 0-5V output signal to be fed into an ADC? With such a large current range, I would recommend taking a look at TIDA-00328, which uses the INA225 along with the comparator of the INA300 to measure a wide current range.  I believe this will be relevant to your application.


    To answer your question, at lower values of Vout, the gain error is not characterized because gain error contribution to overall error is overshadowed by other contributing factors such as input offset voltage.

    Best regards,

    Kareem Moulana

  • 0 in reply to Kareem Moulana
    Expert 2200 points

    Hello Kareem,

     

    Thank you for your reply.

    I think that TIDA-00328  told me will become very helpful for me.

    However, we have a clear target in the following manner.

    Vin is 16V from 9V,In order from the top, MOS, shunt resistor, it bconnect the load.

    The shunt resistor is 3.3mohms.

    We want to detect when the load is open destruction, but the criteria is 30Ω.

    And, the accuracy we are aiming to 0.5%.

    At Vin is 9V, the current through shunt resistor is 300mA,

    Vsense of INA225 is 0.99mV.

    If gain is 50V/V, Vout will be 49mV.

    I want to know meet the 0.5% accuracy at Vout is 50mV.

    Even if it don't meet the accuracy, we want to define for accuracy.

    Is there opinion should estimate how much margin gain error when the output voltage is 50mV?

     

    Best regards,

    Tomoaki Yoshida

  • 0 in reply to Tomoaki Yoshida
    TI__Intellectual 2480 points

    Tomoaki,

    Offset and related errors, like CMRR/PSRR will dominate the error term for small inputs.  Shunt resistor tolerance and Gain Error will dominate the error term for larger inputs.

    In your case, you have a small input of 990μV on your lower end, and so it is offset error (and related errors) you should be concerned with and not gain error.

    I am assuming you have a supply voltage of 5V and so PSRR can be largely ignored, and that your set up is at room temperature (T=25 °C) so that offset drift can follow suit.  Taking these into account, offset voltage and common mode error will give you approximately 15.25% error, while gain error is negligible (maybe 0.0008% contribution to total error).

    I would again recommend taking a good look at TIDA-00328 and seeing how you can incorporate it into your application.

    Best regards,

    -Kareem Moulana