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INA226 I2c read time is abonormal

Lucifer
Expert 2600 points
Other Parts Discussed in Thread: INA226, INA226EVM

Dear Sir,

 I am using INA226 for measuring  our 3.3V pwoer as  a  sensing tool. the tolpology we use is High side current dectection.

When the VBUS=3.3V , VS=3.3V the I2c read the value  every 200mSec and it works pretty well.

But once we switch off the VBUS voltage (VBus=0V), keep VS=3.3V, the I2C read is abonormal. it reads the value evry 5sec~20sec.

Is any problem? It seems somthing wrong. please give me a hand, let me know how to deal with it? Thansk.

  • 0
    TI__Prodigy 380 points
    Dear passerby,

    I just made some measurement with our INA226EVM board. Everything worked fine. I had no issue measuring the input either it's 3.3V or 0V and so in the same time period. I expected this result since there is no direct link between the I2C part and the sensing part.

    To read data from the INA226, a master has to initiate the data transfer. This master lead the reading and then the time between each sample. You probably use a microcontroler connected to the INA226?

    Could you send us your schematic and the code you use in the microcontroler to read the data?

    Best regard,
    Aymeric Nicolas
  • 0 in reply to Aymeric NICOLAS50
    Expert 2600 points

    Dear Sir,

    I am enclosing my design schematic as below.

    www.seawalk.com.tw/.../1.html

    as the schematic above, we measure 3.3v voltage from a buck MP8864 vout.

    once we use EN pin (pin 3) to shutdown the  MP8864  then  INA226 read value slowly. try enable Pin 3 the MP8864 go back to normal.

     Is any problem for this application?  Thanks,

  • 0 in reply to Lucifer
    TI__Prodigy 380 points
    Dear passerby,

    I need some more information from different aspects.

    Analog:

    1) You are doing a high side measurement and the load you try to sense is connected to SLOT_3V3, right? Can you give me more schematic on what is connected to this pin?
    2) Just do be sure, there is no link between the power supply VCC_3V3 and 3V3, right?

    Digital:

    1)On the first post you said the I2C is abnormal and now you said the INA226 reads value slowly when the buck is shutdown. Can you clarify this point? is it a problem of acquisition time which is too long or a problem when you try to access data and the part answers after a delay?
    if it's a problem to accessing data I need more information on your I2C master.

    Best regards,
    Aymeric Nicolas