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INA290: 5mA level accuracy current sensor solution

Part Number: INA290
Other Parts Discussed in Thread: INA228, INA236, INA190, INA229

Hi Team,

My customer is investigating a 5V rail / 5~650mA(Imax) level current sensor solution, they would like to design an sensor can sense low to 5mA with high accuracy, BW is don't care here.

  1. Do you think INA290 is a good choice here ?
  2. If I select  A1 devices: 20 V/V, and use 250m ohm precision resistance, 5mA*250m ohm * 20 = 25mV. 
    The VOS of INA290-A1 is 25uV*20=0.5mV. It is really smaller than 25mV, so the result should have high enough accuracy, am I right ?
  3. Compare to digital output solution INA228 or INA236, which one can perform more highly accuracy at 5mA ?\
  4. If digital solution is more better here, could you provide your suggest solution ?

Thank you so much.

Kai 

  • Hi Kai,

    sounds good to me. But as the output voltage swing to ground is limited to 25mV, you might not be able to see a difference between the two conditions

    1. Isense = 5mA

    and

    2. Isense < 5mV.

    Kai

  • Hey Kai,

    Here are my responses to your questions:

    1. If you're wanting more accuracy, and still want an analog device, then the INA190 would be a better choice if you.
    2. Kai has a good point about the worst case swing to ground. you would have enough resolution, but anything lower that 25mV and you may not be able to detect it. It's also important to note other error sources and noise level.
    3. The INA228 (I2C) and INA229 (SPI) are our most accurate digital current sensors that we have, and would perform better at 5mA than the INA236.
    4. If you want the best solution possible here, then you may want to look into the INA228/9, as they have a lower IB and are highly accurate.  Since you don't care about bandwidth, you'll want to use a longer conversion time and built in averaging to get an even more precise result.
  • Hi Kai, Slight smile

    Thanks for the reply! 

    Kai

  • Hi Mitch,

    Thanks for your input, let me discuss with customer and then feedback to team!

    Kai