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INA219:Calibrating INA219 for different shunt resistor

Part Number: INA219

Hi , 

what is the calibration value for the following configuration

R shunt = 0.001 ohm

Max_Expected_I = 3A

I calculated the result according to datasheet as bellow

Cal =  trunc [ 0.04096 / (0.0001*0.001) ] = 409600 (DEC) = 110 0100 0000 0000 0000 (BIN)

But calibration register only consists of 2 bytes

how can I enter calibration register ?

  • Hello Austin,

    Thank you for using the TI forum. Although you did the calculation correctly, The reason you got a Cal value out of the register size range is because the chosen shunt resistor is not a good size for this application. Using the the error analysis tool on the product page and using the A version with some assumed values in the calculator with a 2mΩ shunt, we get:

    From this tool, you can see that the error is very high. If you change the shunt to 10mΩ, then you error improves quite a bit:

    This brings your Cal value to 40960, which will fit in the register.

    I recommend looking at our "Getting Started with Digital Power Monitors" app note found here: https://www.ti.com/lit/pdf/sboa511. This document also has a link to a calculator tool to help pick the shunt resistor. 

    Regards,

    Mitch

  • Thanks for your information

  • Hi Mitch,

       is there a default setting for the calibration register? Do I need to program calibration register before reading power from it?

    Thanks,

    Tony

  • Hey Tony,

    The default value for the calibration register is 0, and the calibration register does need to be programmed before the registers will update, per the datasheet:

    Regards,

    Mitch