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Original question:

RTOS/INA223: INA223 Equation2 and Power Modes description

RTOS/INA223: PC Field

5782384
Prodigy 10 points
Part Number: INA223

Tool/software: TI-RTOS

Hi there,

INA223 is selected as a power detector.

We are quested to calculate the accuracy of system power under 100%, 80%, 60%, 40% 20%, 10%, 8%, 5%, 3% of Pmax.

Would you please give us the max error(offset) of power gain?

Power measurement error column is shown +-1,5%FSR under VSENSE = (VIN+) – (VIN–) = 10 mV, VS = 3.3 V, and VIN+ = 12 V,
what does the mean of %FSR?, How to calculate FSR of 1.5%?

My conditions are shown in the following

VIN=12V

Pmax = 90 watt

Rshut = 10 mohm

Current shunt voltage gain = 128 V/V

Bus voltage gain =0.1V/V

Power gain = 4.267

Thanks for your help!

CY Hou

  • 0
    TI__Mastermind 23695 points
    Hello CY Hou,

    Thanks for considering to use Texas Instruments. I am looking into your issue right now. To answer your questions, I need to get a few details from our design engineers. As such I will try to have an answer for you tomorrow.
  • 0 in reply to Patrick Simmons
    TI__Mastermind 23695 points

    Hey CY Hou,

    %FSR translates to Percent full scale range of Vout. The full scale range of Vout is considered over the linear range of operation which corresponds to your supply voltage minus the swing to VS power and minus the swing to GND specifications.

    The power gain is derived from the GBV and GSV settings and a attenuation factor. To derive the POWERgain, you take GBV*GSV/3. As for the max power error or the max voltage delta between the measured output and the ideal output, you would take the full scale vout*max Power measurement error.

    In the excel sheet I show how you can calculate %FSR power measurement error from the various error specifications of the datasheet. The values I get are a little lower than what is in the datasheet, which I believe can be attributed to the total error observed for measurements we took along with us adjusting the scope of variance to what would be expected for a larger sample set.

    From looking at your operating conditions, we think you will need to modify some of your settings to get a proper power measurement. If we look at what the output for simply a bus measurement is, we see 12V*0.1V/V=1.2V, which is acceptable. However if look at what the output for current is, we see 90W/12V*10mohm*128V/V=9.6V, which is well over the Vout max and even the supply max. For the power measurement to be valid, the current measurement must also be within a valid measurement range.

    INA223 Calcs

  • 0 in reply to Patrick Simmons
    TI__Mastermind 23695 points

    Hello CY Hou,

    As I stated above you will need to make some adjustment in your settings. With some tweaking and a defined supply level, I think you should be able to calculate an expected error with the information I provided above.  As such, I presume your issue is resolved and will therefore close this thread.  However, if you do need further support on this topic, please respond below to reopen the thread.