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BQ24295: bq24295 Stand Alone

Martin Risso
Intellectual 470 points
Part Number: BQ24295


When using the bq24295 in "stand alone" mode (no I2C host), what is best to do with the SCL and SDA pins?

Leave them floating? Or do I need to add pull up resistors? Pull up to REGN pin? Pull up to SYSTEM? 

10K resistors?

  • 0
    TI__Mastermind 25800 points

    Hey Martin,

    I would recommend tying the SDA and SCL pins low, just to keep leakage current to a minimum. 

    However, tying high through a 10k to SYS would also work. 

    If you leave them floating, their logic state may fluctuate, but I doubt this oscillation of states could happen in such a way change registers.

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    Intellectual 470 points

    Hi Joel,

    I considered tying them to ground. But LO is the active state for I2C logic so I considered tying them HI. But if the chip tried to pull SCL or SDA LO and they are tied directly HI, that wouldn't be good. So that leaves tying HI through resistors to System.

    For a part that advertises "stand alone" operation possible, I think this should be addressed in the data sheet.

    These days, resistors are practically free, but the pick and place charge isn't.

    Marty

  • 0 in reply to Martin Risso
    TI__Mastermind 25800 points
    Hey Marty,

    Our charger is a slave device for I2C communication, so nothing will happen if there is no clock signal from a master device nor an appropriate slave address provided. Now, I could see that if you have other devices on the I2C lines where pulling down is an issue.

    In that case, you may leave the SDA and SCL pins floating, or pull high. Either way, the charger will not respond unless your host explicitly tries to communicate with the charger.

    And thank you for your input. We may take steps to inform designers how operate the part without I2C. However, please note that the "stand alone" operation refers to a lack of host involvement in the internal charger parameters.


    Thank you
    Joel H