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10uA-100mA, 0.05% Error with IIC interface solution, it seems INA219 can't work fine when the current is less than 1mA

mike Yue
Prodigy 30 points
Other Parts Discussed in Thread: INA219

I want to choose a current sense chip solution with IIC interface, I once choosed INA219, but it can't work fine when the current is less than 1mA, I know that there are solution like PGA218 can meet 10uA-100mA requirement ,but it hasn't IIC interface, is there any alternate solution?

  • 0
    TI__Expert 4915 points

    Hi Mike,

    We currently don't have any solutions capable of achieving such a small error at the mentioned currents.

    I would suggest posting on the precision op-amps forum section. Can you describe your application?

  • 0 in reply to Carlos Silva85
    Prodigy 30 points
    Hi Carlos ,
    Thanks your response.
    In fact, I just want to measure current range from 20uA to 50mA, when the current is less than 500uA, the precision can be 5%, and for mA current, the precision can be 1%-2% precision , I want to read back the current via I2C interface as there is no A/D module in my CPU.
    I test INA219,it can function well when the current is greater than 1mA, while when the current is less than 1mA, the test result deviate too much.This application is used in a test board to measure touch panel current.
    May I know your suggestion regard to this application? Thank you very much.


    Mike
  • 0 in reply to mike Yue
    TI__Expert 4915 points
    Hi Mike,

    Regarding our current sense amplifiers, sadly, I cannot make any recommendations

    The amplitude of the smallest signal to be measured is 2500x smaller than the largest signal. Let's for a second assume a 50Ohm sense resistor is used with a 20uA signal generating a 1mV output and a 50mA signal generating a 2.5V signal. The ADC would require a very precise and stable reference voltage and the signal would likely require buffering before being fed to the ADC. As you can see, this solution doesn't even involve a current sense amplifier, because the range is so high and we're already introducing errors in the sense resistor, buffer stage, ADC and reference voltage, not to mention a 2.5V voltage drop on the sense resistor, which I don't yet know if it is acceptable!

    I suggest you first decide how to measure the current, that is the topology (ideally low side), calculate the maximum allowable voltage drop on the sense resistor and from there either open a new thread on the precision opamp forum, or, assuming my design suggestion above is acceptable, open a query directly with the precision ADC group, explaining you need a device with the specs above and either buffered input or very low input current, as any loading of this signal will result in a large reading error.