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BQ76942: I2C communication

Jingguo Wang
Intellectual 2620 points
Part Number: BQ76942
Other Parts Discussed in Thread: BQSTUDIO, EV2400

Hi, team,

Our customer encountered an issue when using I2C communication, the SDA waveform is as channel 3. they want to know why there will exist a drop in low level, and if there will be some risk because of this phenomenon? And when replicating this issue in our EVM, I find I can't adjust the I2C communication speed, the set value is 100k, but the frequency of SCL is only 25k, could you give some suggestions?

BR 

Jingguo

  • 0
    TI__Mastermind 42060 points

    Hello Jingguo,

    What is this waveform from? From the EVM or the customer?

    If you are using the EVM and the EV2400, I believe the EV2400 will have a slower SCL frequency (Which you may be able to change in the bqStudio settings).

    The scope shot does not show everything. Something weird in that image is that SDA seems to slowly rise and then suddenly jump to the full pull-up voltage, do you know why this may be happening?

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    TI__Intellectual 2620 points

    Yes, the waveform seems weird, and the key point is that why there exist a slow drop in low voltage level? Could it lead to some risk? Customer find the phenomenon in their board, and when replicated in our EVM, they find the waveform is worse.

  • 0 in reply to Luis H. S.
    TI__Intellectual 2620 points

    And another question about the capacitor in REG1 LDO(Cext), the minimum value is 1uF, does it have max value?

  • 0 in reply to Jingguo Wang
    TI__Mastermind 42060 points

    Hello Jingguo,

    No I don't think so. If they have not seen any issues so far, it should be fine.

    On the REG1 LDO, not that I know of, increasing the capacitor would likely just slow-down how fast it can turn on and may cause it to have a slower transient response in case of a fast load transient change.

    Best Regards,

    Luis Hernandez Salomon