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BQ25895: BQ25895 quick charge: 12V on PMID!

Ivan Mercier
Prodigy 40 points
Part Number: BQ25895

Hi all,

I want to charge a phone on PMID while I'm charging a battery with QuickCharge VBUS=12V.

If I refer to this typical scheme above, I'm able to do what I want.

But, if I use a quick charger (VBUS~=12V), I got PMID at the same voltage...problem...

Any idea to solve this?

Thanks a lot

  • 0
    TI__Guru**** 166606 points
    Ivan,

    TI's battery charger topology can EITHER charge a battery when VBUS is applied OR provide power back to PMID/VBUS, not both at the same time. There is only a FET separating VBUS and PMID. When charging, the voltage at VBUS appears on PMID. When power is removed, the boost converter turns on and provides power back to PMID.
  • 0 in reply to Jeff F
    TI__Guru**** 166606 points
    Ivan,

    If you apply 12V to VBUS, you will see 12V at PMID. You could add a buck dc/dc converter, powered from PMID, to provide 5V to the phone connected at PMID. However, if you do this, the bq25895 input power, and therefore charge current to the battery, will be reduced because the bq25895 uses the FET between VBUS and PMID to measure input current for the charger's input current limiting circuit.

    Another option would be to add a 5-V boost converter powered from the bq25895 SYS output.
  • 0 in reply to Jeff F
    TI__Guru 57621 points

    Since no response is received for a while, this thread is considered solved and closed. Thanks!