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BQ76952: IIC waveform is abnormal

Moon Wang
Intellectual 1040 points
Part Number: BQ76952

hi Team,

I tested the waveform from the IIC of BQ7695202:

You can see the abnormal waveform in red circle of the pic. Do you know the possible causes?

And the schematics are below: (The pull up resistors with 8.2kΩ have added in SDA/SDL line respectively in realistic test.)

     

Hope to get your reply.

BR,

Moon

  • +1
    TI__Expert 4465 points

    Hi Moon, 

    The schematic and your pull-up values looks reasonable, the signal also looks very square and vertically aligned which indicates decent RC and timing. The odd waveform for that small amount of time seems to be the SCL (clock) of the communication, which is controlled by the controller (typically an MCU), so I will start with looking at the microcontroller settings. It is a very odd waveform, and maybe the clock screeching configuration is not properly configured by the MCU. I cannot think of anything on the device to do this to the clock as it only operates as a peripheral (receiver), unless is clock stretching's but that waveform is not what it is expected on this case Seems like two devices are tying to control the bus at different logic levels for a period of time, so it might be a configuration setting somewhere on your MCU or other devices on the same I2C bus. 

    Regards, 

    Arelis Guerrero 

  • 0 in reply to Arelis Guerrero
    TI__Intellectual 1040 points

    Thanks a lot for your reply! It is because the MCU clock stretching setup. My customer already solved this problem.

  • 0 in reply to Moon Wang
    TI__Expert 4465 points

    Glad we could help. Feel free to post another post if you need additional support.