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Original question:

INA238: Pull up and pull down resistors on Address pin

INA238: Power and current calculation

Naizeng Wang
Expert 4780 points
Part Number: INA238

Hi team,

As for power and current calculation,we can refer to 8.1.2 Current and Power Calculations and 8.2.2 Detailed Design Procedure in datasheet. But customer proposes another method: 

(1) Configure ADCRANGE=0 or 1

(2) SHUNT_CAL=default value 

(3) Get the value of VSHUNT register and then calculate the actual shunt votlage Vs

Vs=VSHUNT*5 μV/LSB when ADCRANGE = 0
Vs=VSHUNT*1.25 μV/LSB when ADCRANGE = 1

(4) Calculate the actual curernt I=Vs/Rshunt, Rshunt is the resistance of shunt resitor. 

(5) Get the value of VBUS register and then calculate the bus votlage Vb

Vb=VBUS*3.125 mV/LSB

(6) Calcualte the power=I*Vb

Is this calculation method reasonable? 

Nison

  • 0
    TI__Expert 6790 points

    Hi Nison,

    Naizeng Wang said:
    (6) Calcualte the power=I*Vb

    Yes, this method is valid and should yield the same result.

    The device can do this power calculation for you internally if you set the calibration values appropriately for the application using the following equations:

    , and to obtain the power value you would read from the POWER register and use the following equation to get the value in watts:

    But if the customer wants to do this calculation externally in software using the readings from the current and bus registers and applying the necessary conversions, that is also valid.

    Best Regards,

    Angel