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BQ25895: Understanding the nuances of the PMID output

Mike Sprauve
Intellectual 390 points
Part Number: BQ25895

Hi 

I thinking of using the PMID output of the BQ25895 as an input to 15W wireless charger circuit.The circuit requires 5V @3A to meet the design specifications. After combing through the various E2E support forum threads related to the BQ25895, it seems that if I use a USB C power adapter as my input source along with a standard single cell Lithium battery, I should be able to achieve the output desired on the PMID. But as always the devil is in the details and I am wondering what I might be missing after reading the D/S and the forum threads. PS I am also planning to run this in autonomous mode. 

Thanks 

  • 0
    TI__Guru**** 165766 points

    Mike,

    In forward (charge) mode, the PMID pin is the input to the charger's buck converter.  It is separated from VBUS pin by a FET that is used to sense current for implementing input current limit and, when the charger is in HiZ mode, for providing reverse blocking (i.e. no battery voltage at VBUS pin).  So, any voltage applied at VBUS will be at PMID, less a voltage drop of IBUS*RDSON(Q1).  In reverse (OTG) mode, the PMID pin is output of the buck charger running in reverse as a boost charger and provides 5.xV at 3A.

    Regards,

    Jeff