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BQ25895: bq25895 behavior question

Beginner
Intellectual 2431 points
Part Number: BQ25895

Hi,

Question#1.

When bq25895 detect there is VBUS voltage, supposedly OTG function will be disabled. 

What's the detail internal behavior in bq25895 that it will do? Like turn off Q2 or Q3? 

Question#2.

In bq25895 reference design http://www.ti.com/lit/df/tidrk16/tidrk16.pdf , it it possible that we can share the inductor for bq25895 

and TPS61235 because of limited board size? It means there is only one inductor for two devices. Kindly let me know what's the Q4 of bq25895 behavior. 

 

  • 0
    TI__Guru**** 167196 points

    Hi TW,

    Regarding Q1, when VBUS voltage rises above UVLO, the OTG boost converter stops switching (Q2 and Q3 off), the logic changes back to buck mode and then the charger starts charging, assuming /CE bit and pin are enabled.

    Regarding Q2, each converter needs its own inductor.  Q4 is the battery FET.  In buck mode, with /CE enabled and V(BAT)<BATREG, Q4 alllows charge current to flow to the battery.  When V(BAT)> MINSYS, Q4 is also used to measure the charge and termination current for regulation and thermination.  When V(BAT)<MINSYS, the charger also uses Q4 to regulate the current.    With charge disabled either by /CE bit or pin, Q4 prevents current flow from SYS to BAT.  Q4 allows current to flow from BAT to SYS for supplementing system load current as needed.  The charger also has a bit to turn off the BATFET, thereby disconnecting the battery from the charger.

    Regards,

    Jeff