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BQ24055 - setting charging current

j.azz
Prodigy 10 points

I use the bq24055 chip with a dedicated power source so I am not in the need of the USB detection.

As I understood from the datasheet, shorting the charger's d+ and d- pins is sufficient to startup with the (max.) current set by the ISET->GND resistor value.

But after powerup the maximum charging current flowing is around 100mA, toggling the ISET2 pin from GND to floating to GND enables the max. desired current.

Did I misunderstood something an is this the default behavior? If so, does there exist a workaround without the need of additional delay/toggle hardware?

Thanks in advance for Your answer!

  • 0
    TI__Mastermind 31120 points

    The D+ and D- lines should be shorted at or before the VBUS is applied and then it should detect an adaptor.

    Make sure you do not have any signal toggling the ISET2 pin after the power-up or you will hand over control to the ISET2 pin.

    I tried it on the EVM with J7 shorted and it always comes up in fastcharge.  Is your fast charge current set higher than 100mA?  What is your battery voltage...are you in precharge?