INA219: How to calculate 0x05 Calibration value？

Seasat Liu

Intellectual 1040 points

Part Number: INA219

hello team,

I am working on INA219 current sensor for Router current sensing application.

Rshunt = 0.002ohm

Max Expected Current = 15A.

Current_LSB=15A/2^15=457.7uA/bit

Cal=trunc[0.04096/(Current_LSB*R)]=44814

Is my calculation process and results correct?

over 5 years ago

0 Guang Zhou over 5 years ago

TI__Mastermind 34070 points

Hi Seasat,

Yes your math is correct.

We recommending round up the current LSB from 457uA to a nice even number, such as 500uA for two reasons, (1) giving a little more head room with full range slightly >15A; (2) Avoid truncation error in the config value even though this error is negligible for most if not all situations.

With that, I would select a config value of d’40960, or h’A000.

Regards, Guang

0 Seasat Liu over 5 years ago in reply to Guang Zhou

TI__Intellectual 1040 points

Thanks for answering
If we round out 457 μA/bit s to 1 mA/bit according to page 26 of the datasheet, will it cause a large measurement error?

0 Guang Zhou over 5 years ago in reply to Seasat Liu

TI__Mastermind 34070 points

Hi,

The value of calibration register doesn’t affect the shunt value measurement; however it does affect the reporting resolution and accuracy of current. From this perspective, it is better to use a smaller LSB, in this case 0.5mA.

Regards, Guang

0 Seasat Liu over 5 years ago in reply to Guang Zhou

TI__Intellectual 1040 points

HI Guang

Thank you for your reply.
I want to ask a question,
If my actual current is 10A.
If I write according to CAL value 1mA(0x5000), the data read is 10000.
If I write according to CAL value 0.5mA(0xA000). what data will I read? 10000 or close 20000？

0 Guang Zhou over 5 years ago in reply to Guang Zhou

TI__Mastermind 34070 points

Hi Seasat,,

The decimal value will be 20000 if you choose current LSB=0.5mA; compared with 10000 if LSB=1mA.

With these two choices, the calculated ideal current remains the same 10A.

Regards, Guang

0 Guang Zhou over 5 years ago in reply to Guang Zhou

TI__Mastermind 34070 points

Hi Seasat,

If there are no more questions, please close this thread by clicking the “resolved my issue” button.

Regards, Guang

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INA219: How to calculate 0x05 Calibration value？