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INA232: How fast can consecutive reads be performed with the INA232?

Daniel Miller
Prodigy 40 points
Part Number: INA232
Other Parts Discussed in Thread: INA228

I'm completely new to this field so please be gentle.

I'm designing/prototyping a board which needs to read current pulses. I need to identify current variations of at least 10ma with a sequential read rate of at least 300 microseconds each - or say 3000 reads per second. My intended range is from 0-3A, and if I haven't totally misunderstood how to do this I think a 27mOhm resistor is appropriate.

At the moment, I'm using a STM32F103C8 microcontroller if it matters - absolutely not locked in and I'll happily switch if there's sufficient reason to.

My questions: first, is the INA232 capable of the resolution and speed I want? If not - is there an alternative?

And...did I pick the right resistor value? I did 8.192mV / 3 = 27xxx, so rounded down to 27.

  • +1
    TI__Mastermind 30910 points

    Hi,

    With 27mOhm, the INA232 will be able to provide the resolution you need. In addition, the device has a zoom range of 20mV, which provides 4x better resolution if the shunt voltage is within range.

    INA232 can convert as fast as 140uS, therefore it is capable of the speed you need. If you also need to measure Vbus, then the conversion time would double because the ADC makes shunt and bus measurements sequentially.

    INA228/238/237 is another candidate. This family of high voltage devices offer fast conversion (as low as 50uS). In addition, INA228 offers superior accuracy and resolution.

    Please note that longer conversion time and/or larger number of averaging is desired for noise reduction. This would be true regardless which device is eventually chosen. Here is a plot from the INA232 datasheet to illustrate the relationship:

    Regards, Guang