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INA780B: Calibration of the INA780B

Roy Flax
Prodigy 50 points
Part Number: INA780B
Other Parts Discussed in Thread: INA780

Tool/software:

Hi,

1. In the datasheet it is mentioned that the input offset current is 125mA which is very significant in my application, so I need to calibrate it.

* In my circuit I have a power switch in series to the INA780B, so my question is if I can open the power switch, read the measured current from the INA780B, and subtract this value from all the later readings (when the power switch is close and the INA780B it exposed to high voltage and current)?

* If the proposed calibration of the current sensor is OK, what should be the expected accuracy of the current readings?

2. Does figure 5-2 in the datasheet refer to model A and not to model B? If not then it seems that I don't understand what is shown in that graph and its relation to the input offset current data from the specifications which are typical +/-30mA.

3. Are the power measurement of the INA780B calculated by simple multiplication of the current and voltage that it measures?

Thanks,

Roy

  • 0
    TI__Expert 3835 points

    Hi Roy,

    Yes your proposed calibration method will work. As for the accuracy, please refer to the DC accuracy specs in the electrical characteristics table.

    Roy Flax said:
    Does figure 5-2 in the datasheet refer to model A and not to model B? If not then it seems that I don't understand what is shown in that graph and its relation to the input offset current data from the specifications which are typical +/-30mA.

    I'm not sure I understand your question. Figure 5.2 depicts the relationship between quiescent current and frequency. Input offset current and Iq are different parameters - offset current is the difference in input current between the IN+/- lines and the Iq is the current required for the device to be operational.

    Roy Flax said:
    Are the power measurement of the INA780B calculated by simple multiplication of the current and voltage that it measures?

    Yes, and this is mentioned in the datasheet.

    Best,
    Mallika Senthil

  • 0 in reply to Mallika Senthil
    Prodigy 50 points

    Hi Mallika Senthil,

    Thanks for the answers!

    In your answer to my question about figure 5-2, you mistakenly referred to figure 5-20.

    Thanks,

    Roy

  • 0 in reply to Roy Flax
    TI__Expert 3835 points

    Hi Roy,

    I apologize, I did misread the figure number. I'm looking into that, I'll get back to you soon.

    Best,
    Mallika Senthil

  • 0 in reply to Roy Flax
    TI__Expert 3835 points

    Hi Roy,

    I've raised the query with the engineers involved in the INA780, they will look into in and update the datasheet if necessary.

    Best,
    Mallika Senthil

  • 0 in reply to Mallika Senthil
    Prodigy 50 points

    Thank you so much