• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 47 subscribers
  • Views 259 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

INA228_237_238EVM: INA228 EVM

maayan hasson
Prodigy 50 points
Part Number: INA228

Hello

I have a setup utilizing the EVM of INA228.We soldered a 25 mOhm Rshunt and connected an electronic load to the load part, with a VBUS of 5V.

We are encountering two issues that we are struggling to understand.

Firstly, when we adjust the shunt full scale range to a higher option in the GUI, we observe more accurate measurements of current. Conversely, the lower range seems to include all the resistance present near the shunt (such as wires).

Secondly, we're experiencing a discrepancy between the current we input into the electronic load (300 mA) and what is displayed on the GUI (240 mA).

  • 0
    TI__Mastermind 24675 points

    Hello Maayan,

    When you change the ADCRANGE parameter of the INA228, make sure that the SHUNT_CAL is getting updated accordingly, as it will need a different SHUNT_CAL value for each ADCRANGE setting. Also, when you update the ADCRANGE setting from the configuration tab, make sure it is actually updated in the register map settings. This should change automatically, but I've seen a bug sometimes where this doesn't change automatically in the register map. That being said, the measurement from the shunt voltage register readout should be very similar between the two setups, so you can use that to confirm as well (just make sure you use the correct LSB for each range setting).

    There are many reasons why this value may be different. One possible reason is that the actual current from the load is different than expected. Another possible reason is that the shunt resistor has more error than anticipated, causing the measurement to be mis-interpreted. To check for this, you can measure the voltage directly at the IN+ and IN- pins with respect to the ground pin of the INA228, and confirm that the shunt voltage register matches the measured value. You can also try to measure the resistor value and use that exact value in the SHUNT_CAL calculation. 

    Regards,

    Mitch

  • 0 in reply to Mitch M
    Prodigy 50 points

    Hi Mitch

    After following your suggestion and adjusting the SHUNT_CAL according to the change in ADCRANGE, we're still encountering an issue. In the lower range, we're getting a current reading of 0.05 (while expecting 0.2), while the higher range yields the correct current. What steps can we take to address this problem

    Maayan

  • 0 in reply to maayan hasson
    TI__Mastermind 24675 points

    Hey Maayan,

    Can you send me a readout of all register values during the low range measurement, as well as your shunt value and expected maximum current used for the SHUNT_CAL calculation. It may also be helpful to send me the readout with the high range measurement for comparison.

    Also, you can check the value from VSHUNT value during the lower range (with the LSB for the lower range) to confirm if it is as expected. (this way the calculations for the current register won't matter)

    Regards,

    Mitch