• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 47 subscribers
  • Views 1284 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

Issue with INA226

Lars Warnke
Prodigy 30 points
Other Parts Discussed in Thread: INA226, AMC1203

Hey there,

I have a problem with the INA226. We use it to measure the current of a motor Phase,please see the attached file for schematic and PCB layout.

When we turn on both the supply and the Motor, the INA226 gets quite hot. We measured it at almost 100°C. I already figured out, that there is a considerable voltage drop over the two 10Ohm resistors, so I guess the INA is drawing more current than it should. We already replaced the INA's and it did not improve. Can you help me to find a solution for this problem?

Kind regards,

Lars

8055.INA226_Layout.pdf

  • 0
    TI__Genius 14825 points

    Lars,


    The first thing that stands out to me about your schematic is that you have PGND and DGND, and the shunt resistor power supply operates with respect to PGND but the INA226 is tied to DGND.  Is there potentially a large difference between PGND and DGND?  This may be the culprit but I'll wait for your response and in the mean time I'll float this by some of the engineers here and see what they think about the setup.

    Other things I notice are that the VBUS is connected to the VIN+ pin after the filter.  I don't think this makes much difference but it's not how we show it in figure 22 of the data sheet.  Per the data sheet, the VBUS line has an impedance of 830kohms so I doubt much current is flowing into it at all.

    Is there any chance the common mode of the inputs is swinging below -0.3V or exceeding +40V?  Just another thought.

    So, let me know about the PGND/DGND discrepancies and I'll see what I can find out in the mean time.

    Thanks for using the INA226!

    Jason Bridgmon

  • 0 in reply to Jason Bridgmon
    Prodigy 30 points

    Hi Jason,

    thank you for your quick Response. We did some further measurements today:

    Jason Bridgmon said:
    Is there potentially a large difference between PGND and DGND?

    When switching the MOSFET's there is Noise @ 0.5V between PGND and DGND.

    Jason Bridgmon said:
    Is there any chance the common mode of the inputs is swinging below -0.3V or exceeding +40V?  Just another thought

    This seems to be the real Problem. When switching the MOSFET's from high to low, there is a negative Voltage @ -0.9 to -1.1V with respect to PGND. We did a small Simulation on the MOSFET's and the Simulation showed similiar behavior.

    Do you have suggestions how to solve this Problem?

    Kind regards,

    Lars

  • 0 in reply to Lars Warnke
    TI__Genius 14825 points

    Lars,

    One idea that came up to handle the below-GND voltage is to increase the filter resistors (R26 and R27 on your schematic).  You could try going up to 100ohms and see if that is enough to limit the current into the device, at the possible cost of gain error and maybe other effects, but it's easy to try without any layout changes.

    We're still looking into other options, but we hope this is something to get you going and if it works well for you, great!


    Regards,

    Jason Bridgmon

  • 0 in reply to Jason Bridgmon
    Prodigy 30 points

    Jason,

    I'm sorry but this did not work also. We will continue to work with the AMC1203. This device Looks like it would better fit to our application.

    Thank you for your Support!

  • 0 in reply to Lars Warnke
    TI__Genius 14825 points

    Lars,

    I do apologize for being unable to get your issue resolved, but I'm glad the AMC1203 is working out!

    regards,

    Jason Bridgmon