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BQ78350-R1: Cooperate with bq769300

liu zhening
Prodigy 35 points
Part Number: BQ78350-R1
Other Parts Discussed in Thread: BQ78350, BQ76930

Hello, when my is using bq78350r1 and bq7693000 to charge the battery, I don't know why I can't communicate to bq78350 through SMBus. I monitor the IIC interface through the logic analyzer and find that bq769300 has no corresponding signal of bq78350 and 78350 is constantly restarting. After replacing the bq769300 chip, everything returned to normal. The following is the schematic diagram. I hope you can get help.

thank you very much indeed

6052.Schematic Prints.pdf

1854.gg.csv

  • 0
    TI__Guru* 77283 points

    Hi Liu,

    How many series cells are used in this battery? On connector J1, it looks like there are 5 cells? A minimum of 6 cells are needed for the BQ76930. 

    Are you using BJT transistors for balancing? I think FETs are needed for this device. It would be good to monitor the REGOUT pin of the BQ76930 to see if the voltage is stable since this powers the BQ78350.

    Regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 35 points

    Hi Matt:

    This battery pack is connected in series with 6 batteries. There is indeed a separate balanced FET, but I use PNP triode here. I wonder if this is the reason?

  • 0 in reply to liu zhening
    TI__Guru* 77283 points

    Hi Liu,

    I am not sure if this is related to the issue you observed, but I have not seen PNP triodes used before so I don't know if there will be any issues with balancing. 

    When the BQ78350 was constantly restarting, can you describe the issue in more detail? Was the power cycling on REGOUT of the BQ76930 (VCC pin of BQ78350)? 

    Thanks,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 35 points

    Hi Matt:

    The REGOUT power supply has not been reset. Checking the iic pins of the 78350 and 769300 through a logic analyzer found that the 769300 did not reply to any data from the 78350. At present, the problem has been solved, because the current injected into the transistor caused the damage to the 769300

    Thank you for your attention, have a nice day

  • 0 in reply to Matt Sunna
    Prodigy 35 points

    Also I want to confirm, how to manually check if the balance of 78350 and 769300 is enabled properly。Can I manually operate the 78350 to turn on the balance function?

  • +1 in reply to liu zhening
    TI__Guru* 77283 points

    Hi Lui,

    The balancing function is autonomous when using the BQ78350. So you have to meet the balancing conditions to see the balancing enabled (charging current detected, cell voltages higher than start voltage, etc.).

    Best regards,

    Matt