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INA220 spec question

Luke Sun
Intellectual 1830 points
Other Parts Discussed in Thread: INA220

Hi team,

My customer has some question on INA220 spec, which really needs your guidance.

1. What's the definition of "current sense gain error" and "current measurement error" in characteristics table? What's the difference of them?

2. What's the definition of "ADC shunt offset" and "ADC shunt gain error" in datasheet figure plot? What's the difference of them?

Thanks for your help!

  • 0
    TI__Genius 15760 points
    Hi Luke,

    Current sense gain error reflects the accuracy of the shunt voltage readback (register Pointer x01)
    Current Measurement Error reflect the calculated value in Current readback (register Pointer x04), and requires calibration by the user.

    ADC shunt Offset error is what the output reads with the input at 0 Volts; if 0Vin yields 20uVOut, then it has 20uV offset (g=1)
    ADC Gain Error is when a voltage is applied; I think in this case +/- 32mV at Gain= 1

    Offset is measured without any input voltage, Gain Error is measure using differential input voltages. Our gain error measurement techniques nulls the offset voltage that might be present.

    See section 8.5.1 in the data sheet for Current measurement
    See section 8.5.3 in the datasheet for Shunt voltage readback

    Hope this helps!
  • 0 in reply to Mayrim Verdejo
    TI__Intellectual 1830 points

    Mayrim,

    Thanks for your reply!

    I have a following question:

    For the current sense gain error and current measurement error, Current sense gain error is +/-40m% only, and Current measurement error is +/-0.2%.

    But Register 0x4 is only the product of register 0x1*calibration value. They should have the same error number.

    Why the number has a big difference in the datasheet between these two errors?

    Is the error introduced by the calculated calibration value?

  • 0 in reply to Luke Sun
    TI__Intellectual 1830 points
    Hi Mayrim,
    Any reply?
    Thank you!
  • 0 in reply to Luke Sun
    TI__Genius 15760 points
    Hi Luke,

    Numbers did not made sense to me either so I asked our designers and systems engineer to explain the parameter for me. It turns out that total measurement error is the combination of offset and gain error.

    Current measurement error = (Worst case Offset/Vshunt) + Gain Error = (40uV/32mV ) + 40m% = 125m% + 40m% = .165% ~~~aprox. 0.2%

    Regards