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INA190EVM: How to set-up this EVM when measuring few uA to 30mA current?

ArTzy
Genius 16019 points
Part Number: INA190EVM
Other Parts Discussed in Thread: INA190

Tool/software:

Hi Experts,

Using the INA190EVM board, may I know what gain variant and value of shunt resistor to use when reading a uA to ~30mA current?

Also, what other filter components on the board need to populate and what values?

Thank you.

Regards,
Archie A.

  • 0
    TI__Genius 16019 points

    Hello Experts,

    Reviewing from Section 8.1.2 RSENSE and Device Gain Selection, from the equation provided to prevent setting output beyond output swing, when using the following setting of the board:

    Vs: 5V
    GAIN: 500
    Max current: ~30mA
    Min current: ~10uA

    The Rsense to use will be around 0.25Ω (0.6mW) to have a better input differential voltage.

    Only this component is needed to proceed the evaluation, correct?

    Thank you,
    Archie A.

  • +1 in reply to ArTzy
    TI__Mastermind 32345 points

    Hey Archie,

    10uA to 30mA (dynamic range = 3000:1) may not be possible with just one INA190. You may need two INA190. For example one INA190A5 to sense 10uA to ~5mA and another INA190A1 to sense ~5mA to 30mA.

    INA190 output dynamic range is only about 500 = 5V/0.01V assuming a minimum 10mV VOUT at low current level.

    Next problem is the size of shunt resistor. 0.25Ohm*10uA=2.5uV. The INA190A5 (500V/V) would amplify to 1.25mV. This is a very small signal given the few mV of noise on INA190 output. If you cannot increase this minimum signal, then you will need to provide a small bias voltage to REF pin(~>50mV) to keep VOUT from saturating into GND rail when current is low.

    Given small signal and noise I ideally recommend increasing the shunt resistor as large as possible/allowable for system.

    Next, decide what the minimum allowable BW so you can place input and output filters with lowest allowable fc. This to reduce noise floor as low as possible to you can resolve smaller signal and thus use a smaller shunt.

    I actually go over this noise/BW trade off in this post where you can use TINA simulation tools to determine best balance. Also here is a circuit note on measuring low currents with INA190.

    https://e2e.ti.com/support/amplifiers-group/amplifiers-internal/f/amplifiers-internal-forum/1435670/ina310a-q1-sensing-current-accuracy-and-quiescent-power-in-12v-auto-bms

    https://www.ti.com.cn/cn/lit/an/sboa551/sboa551.pdf 

    Sincerely,

    Peter

  • 0 in reply to Peter Iliya
    TI__Genius 16019 points

    Thank you, Peter.

    The customer actually didn't mention the minimum and just stating few uA up to 30mA.

    Let's see if 0.25 ohm still feasible on their design and very much open for your suggestions. They want to design a current meter to their mini-solar panel that provides power with such small current.

    I am seeing this related post as well that you supported:

    Thanks for your guidance.

    Regards,
    Archie A.