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BQ25895: Can boost activated without adapter connected?

Ben Huang1
Intellectual 705 points
Part Number: BQ25895

Hi  Sir 

According to datasheet (8.2.5 Boost Mode Operation from Battery)

 

VBUS (Adapter plugged in) is necessary for boost mode operation.

In power bank application, is it impossible to charge the portable device without adapter connected? does it make any sense? Or that is only my misunderstanding

Thanks for comment !

Regards

Ben

  • 0
    TI__Guru**** 165886 points
    Hi Ben,

    Boost operation, with output on the PMID pin, occurs only if the external voltage at VBUS is below V(BAT) + sleep threshold, as well as the other conditions listed in 8.2.5. This happens if there is no adapter at VBUS.
  • 0 in reply to Jeff F
    Intellectual 705 points
    Hi Jeff

    Thanks for comment!


    1. If no adapter plug in, which source can supply the VBUS ?
    2. According to Functional Block Diagram

    No matter what boost or buck mode operation is, REGN LDO must be activated first right?

    VBUS is the input of REGN LDO under buck mode, but is VBUS still the input of REGN LDO under boost mode (VBUS is not high-voltage rail at this moment (VBUS is below VBAT + sleep threshold)) ?


    Can VBUS keep REGN LDO in regulation under boost mode?


    Should I miss something inside datasheet?

    Regards
    Ben
  • 0 in reply to Ben Huang1
    TI__Guru**** 165886 points
    Ben,

    REGN is powered from PMID.
  • 0 in reply to Jeff F
    Intellectual 705 points
    Hi Jeff


    Thanks for reply!

    Actually I don’t understand why REGN is powered from PMID.
    I read EVM user guide and find the section “ Boost Mode Verification”
    As the fist step mentioned, turn off and disconnect power supply @ VBUS (which is equivalent to no adapter plugged in)

    I may realize the system behavior via EVM
    Can EVM work standalone without I2C host? There may be a SW installation issue


    Regards
    Ben
  • 0 in reply to Ben Huang1
    TI__Guru**** 165886 points
    Ben,

    Yes, the EVM works in standalone mode with default values.