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BQ25120: BQ25120 i2c can interface can disable in the middle of i2c transaction?

Philip Gruebele
Prodigy 140 points
Part Number: BQ25120

Hi.

I have a product prototype with the BQ25120.  The problem I have is that according to the spec, if VIN is valid, charging is disabled when CD=1, therefore requiring CD=0 during charging. However, I need to occasionally read i2c registers during charge (perhaps even read battery voltage), and if during such a read VIN becomes 0V, then charging will stop and CD=0 will cause i2c to be disabled and my i2c transaction to fail.  This complicates things considerably since I cannot count on reliable i2c during charge (since CD has to be 0 during charge).

Am I understanding this correctly?  How would one go about implementing reliable i2c communications during charging/topping which are not affected by loosing VIN? It seems strange that i2c enable is not controllable in a deterministic way...

Thanks

Philip

  • 0
    TI__Genius 12485 points
    Philip,

    The way you would have to code is if VIN is not present, you would need to raise CD high before starting an I2C and lower it back to go to HiZ mode.

    Are you using the PG pin? You could "get status" on the PG pin to determine that. You could also read status in order to see if VIN present and if nack, you can raise the CD pin to begin transaction but I prefer the PG method better.



    thanks,
    Gautham