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BQ25606: What happens if a input power is connected to the VBUS pin while the chip is working in boost mode?

Geraldo Gomes
Intellectual 365 points
Part Number: BQ25606
Other Parts Discussed in Thread: BQ25616, BQ25619

Hello,

I would like to design a battery system using the BQ25606. This system must supply a load of 5V/500mA with energy from a single cell 18650 lithium battery when there is no AC adapter connected. When an AC adapter is connected this load must be powered from AC adapter while the battery is charged also from AC adapter.

Reading the datasheet, I understood that the output of the BQ25606 boost is the VBUS pin, and this pin is the same to input power to charge the battery. So, I would like to know what will be behavior of the BQ25606 when it is working in boost mode and an AC adapter is connected in the VBUS pin.

Could you help me?

Thanks,

Geraldo Gomes.

  • 0
    TI__Guru 57781 points

    Geraldo,

    We are working on it and will get back to you.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Intellectual 365 points

    Thanks for your reply Ning,

    In addition, I would like to understand other questions:

    1) How the PMID and RBFET works in buck mode (charging battery) and boost mode?

    2) Is possible to get RBFET off (VBUS off) in boost mode and get the 5V/1.2A output in PMID pin during boost mode?

    My questions above are related with my application, I intend to connect the load in the PMID pin, and when the AC adapter is not present, I would like the boost power my load connected in the PMID pin while the RBFET is off to avoid leakage of current to the input connector off my board. When an AC adapter is present, the RBFET must be ON the allow voltage in PMID pin and power my load while the buck works to charge the battery. How can I achieve this desired behavior with the BQ25606?

    Best regards,

    Geraldo Gomes.

  • 0 in reply to Geraldo Gomes
    TI__Expert 5590 points

    Hi Geraldo:

    Please see my answer below in the text:

    1) How the PMID and RBFET works in buck mode (charging battery) and boost mode?

    For BQ25606, in Boost mode, when Boost is enabled, RBFET is fully on. The same is charge mode. 

    2) Is possible to get RBFET off (VBUS off) in boost mode and get the 5V/1.2A output in PMID pin during boost mode?

    No for BQ25616. I would recommend BQ25619 that has the feature with PMID output with RBFET off. 

    My questions above are related with my application, I intend to connect the load in the PMID pin, and when the AC adapter is not present, I would like the boost power my load connected in the PMID pin while the RBFET is off to avoid leakage of current to the input connector off my board. When an AC adapter is present, the RBFET must be ON the allow voltage in PMID pin and power my load while the buck works to charge the battery. How can I achieve this desired behavior with the BQ25606?

    Yes, BQ25619 can meet your requirement. Thanks. 

  • 0 in reply to Hong Mao
    Intellectual 365 points

    Hello Mr. Hong Mao,

    Very thanks for you reply! Thanks for your suggestion!

    One more question about the BQ25606, if the RBFET is always ON, what happens if I plug an DC adapter with voltage greater than 5V during the boost mode?

    Greetings,

    Geraldo Gomes.

  • 0 in reply to Geraldo Gomes
    TI__Expert 5590 points

    Good question, yes, RBFET is always on. If the voltage you applied does not trigger OVP which is about 6.4V, Boost keeps on. VBUS cannot detect adaptor plug-in. For BQ25619, the converter will switch from Boost mode to charge mode for this condition because RBFET is off during Boost.