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INA226: Need to sense current from 1mA to 1000mA with a resolution of +/-1mA, is the INA226 the best choice?

Jim Tassitano
Prodigy 140 points
Part Number: INA226
Other Parts Discussed in Thread: INA219, INA220

Hi,

I need to sense the current from a +12VDC supply with a resolution of +/- 1mA and a range of 1mA to 1,000mA. The accuracy needs to be 1%. I was thinking of using the INA226 for 2 reasons, it has an external shunt and has an I2C interface. The data sheet shows a 2milliOhm shunt resistor. I assume I can increase this value since I don't need the 10Amp range. There are 3 power supply circuits I need to monitor the current on so I would need 3 of these parts. Here are my questions.

1.  What value shunt resistor should I use for 1Amp full scale?

2. Is there a less expensive part or parts I can use for this?

  • 0
    TI__Mastermind 26335 points

    Hello Jim,

    Thanks for your interest in current shunt monitors.  Since your max current value is 1000x larger than your min current value, you will want to use the entire allowable shunt voltage range of 81.92mV to mitigate the error sources that can effect the accuracy of low value measurements.  We assume that this voltage will be generated when the max current (1A) is across your shunt.  Consequently, I would use a 82 mohm shunt or slightly smaller to account for resistor tolerance.  With that shunt we can get an idea of what kind of error you would expect over your range of measurements using the online calculator (shown below) that can be found on the right side of the INA226 product page.

    Alternative parts that you might consider are the INA220 and INA219.  However, these will have lower accuracy at the lower part of your measurement range.