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BQ25895 to instead adapter

Kai Hsiao
Guru 12675 points
Other Parts Discussed in Thread: BQ25895, BQ24297, BQ25890, TPS22953

Dear Sir 

Our customer would like to use BQ25895 to do dual battery pack application 

As below structure 

If adapter remove ,BQ25895 will boost 5Vout/3A through PMID pin to instead adapter to supply power to BQ24297 or BQ25890

My question is ,is it possible to use red direction to supply BQ24297 or BQ25890 ?? Such as we can omit 1pcs TPS22953

But I need to confirm if adapter re-insert to system ,BQ25895 can be changed charger mode and without any problem

Thanks  

 

  • 0
    TI__Guru*** 143880 points

    If I understand correctly, your customers wants to connect:

    bq25890/bq24297 BAT to charge 1st battery when adapter connected

    bq25895 BAT to charge 2nd battery when adapter connected

    bq25895 PMID to bq25890/bq24297 VBUS so 2nd battery can charge 1st battery when no adapter is connected

    bq25895 automatically returns to charge mode when VBUS > UVLO is applied.  You will still need reverse blocking between 895 PMID and adapter when the adapter is connected.  A low RDSON PFET and low cost NFET configured as below should work:

    PFET D - adaptor

    PFET S - 890/297 VBUS

    PFET G = NFET D with pull up resistor to VBUS

    NFET S - GND

    NFET G - adaptor with pull down resistor to GND.

  • 0 in reply to Jeff F
    Guru 12675 points

    Dear Jeff

    Yes!! your explain is correct 

    But as you mention ,if BQ25895 is doing boost mode and TPS22953 will supply 5Vout

    At this moment ,BQ25895's VBUS > UVLO ,so does BQ25895 change to charger mode automatically ??

    I think I need force BQ25895 into boost mode ,when adapter is not existed ,

    bq25895 automatically returns to charge mode when VBUS > UVLO is applied.  

  • 0 in reply to Kai Hsiao
    TI__Guru*** 143880 points

    bq25895 will not enter boost mode if VBUS > UVLO.