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Can I drive I2C lines of bq24765 high when bq24765 is not powered i.e. DCINA is not available?

Bipin Bopaliya
Prodigy 160 points
Other Parts Discussed in Thread: BQ24765

Hello,

 

We are working with bq24765 battery charging controller. I want to drive pull ups of bq24765 ICs lines with external 3.3V supply (small LDO) and not from VREF of bq24765. This is because I want to operate this I2C line even when bq24765 is not powered.

My queries are as follow:

  1. Can I drive I2C lines of bq24765 high when bq24765 is not powered i.e. DCINA is not available?
  2. Do I need to connect VDDSMB ( Input voltage for SMBus logic) to external 3.3V supply? 

Regards,
Bipin

  • 0
    TI__Guru 56650 points

    1. Yes. You can drive I2C lines of bq24765 high when bq23765 is not powered. But, the bq24765 can not receive any command from SMbus at that condition.

    2. If the 3.3VREF of bq24765 is not available, the SMBus of bq24765 doesn't work. So, you don't need to connect VDDSMB to external 3.3V supply.

    FYI: VREF regulator and VICM current sense amplifier are active when ACIN pin voltage is greater than 0.6V and DCINA>VDCIN_UVLO. (See page 3rd )

    If you want 3.3VREF available without adaptor input, the BAT has to be connected to DCINA (DCINA>VDCIN_UVLO) and bias ACIN voltage to 0.6V~2.4V range.

  • 0 in reply to Wang5577
    Prodigy 160 points

    Thanks Wang.

    It clears my requirements. I already have LDO available on PCB so do not need VREF available when ACIN is not available. My only confusion was weather to connect VDDSMB with external supply or not.

     

    Regards,

    Bipin

  • 0 in reply to Bipin Bopaliya
    TI__Guru 56650 points

    VDDSMB can be connected to an external 3.3V external supply.