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Original question:

INA186: INA186

INA186: need device to detect 1~10mA

Yanni Li
Intellectual 1960 points
Part Number: INA186

Hi team,

We have a customer inquiring about the INA186. Below is the verbatim of his inquiry:

 I want to use INA186 to detect 1~10mA current. If I design the circuit according to 8.2 Typical Applications in the datasheet,

could you please advice the value of Rsense and the device gain

I want to set the AD resolution of MPU to be 10bit, and Vout=0.1uA/mV, thank you very much.

  • 0
    Guru 140200 points

    Hi Yanni,

    10mA / 0.1µA = 100,000. Hhm, does not go together with a 10bit ADC?

    Kai

  • 0
    TI__Mastermind 18780 points

    Yanni,

    For a Vs of 5V, around a 20Ω shunt resistor looks like it should provide optimal performance with the INA186A1 here (a shunt of this size may be used with this device as the front end input impedance is in the region of MΩs). With this, the entirety of the range (1mA-10mA) exhibits an error of around 1%, which is the worst case gain error of the device. If accuracy greater than this is needed, you may need to look at the INA190A1, as the gain error is the best case error that can be achieved, and this is a datasheet parameter, i.e., there is no way to circumvent this. Be aware of the swing to rail limitations of the device and make sure the resistor selected accounts for this, as 20Ω assumes the ideal 5V out. At this level, maximum power dissipation is 2mW, so power should not be an issue.

    I also agree with Kai that digitization of this signal is probably going to need to be greater than 10-bit precision if you are hoping for 0.1uA/mV conversion. For a 10-bit ADC, for a 5V VCC, the LSB of this resolution is only 4.88mV, nowhere near the resolution you are hoping to achieve.