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BQ25886: Timing specification for changing Battery to Vbus input transition

Satoshi
Guru 19645 points
Part Number: BQ25886
Other Parts Discussed in Thread: BQ24171,

One customer hope to get timing spec for transition time of changing Battary input to VBUS input. (SYS is always output)

Is there spec data for below contents?

①BAT to VBUS transition time and SYS output off time on these timing

②Timing graph: For example, best is the bq25886 version for bq24171 figure 7~11

③Reverse version; ①② data for changing VBUS input to BAT input 

Best regards,

Satoshi

  • 0
    TI__Guru**** 165886 points

    Hi Satoshi-san,

    The BQ24171 and BQ25886 have different powerpath architectures.  The BQ24171 has to ensure that the BATFET is not on when the ACFETs are on, so there is a break-before-make delay.  With the BQ25886 NVDC powerpath topology, the SYS output must come through the buck converter.  For example, when only battery is attached, V(SYS)=V(BAT)-IBAT*RDSonQ4.  When power is attached, V(SYS), clamped at V(BAT)-IBAT*RDSon, rises to either MINSYS or VBATREG+~50mV, as shown in d/s figure 14, assuming no DPM.

    I will look for scope shots in our validation test files but more than likely, I will need to take new scope shots.  Unfortunately, we are having to time share access to the lab due to COVID-19 restrictions.  The scope shots may be delayed several days or even a week.

    Regards,

    Jeff   

  • 0 in reply to Jeff F
    Guru 19645 points

    Jeff-san

    Thank you for reply,

    I understood your situation for COVID-19.

    I looking forward your update.

    Best regards,

    Satoshi

  • 0 in reply to Jeff F
    Guru 19645 points

    Jeff-san

    Sorry for additional question,

    Is bq25886 have Vsys time lag (Output off time)  on transition battery operate to adapter input?

    Customer is worrying about; when time lag is large and high battery current condition, Vsys become voltage drop. 

    Best regards,

    Satoshi

  • 0 in reply to Satoshi
    TI__Guru**** 165886 points

    Satoshi-san,

    No lag time.  Hopefully the attached plots in zip file are accessible and answer your customers questions.  For all plots, VBUS=5V, ICHRG=900mA.  With IINDPM=1A, the charger is running in IINDPM in all the plots.

    Regards,

    Jeff886-startup_and_transient_dips.zip.zip 

  • 0 in reply to Jeff F
    Guru 19645 points

    Jeff-san

    Thank you for attached data,

    Please let me confirm two points below for you attached waveform;

    ①About waveform; light blue: Vbat and purple: Vsys, correct?

    ②One customer's important point are change timing for VBUS⇒Battery drive, and Battery drive⇒VBUS.

    　I think that waveform mean VBUS⇒Battery: name "886-powerdown ~" and Battery drive⇒VBUS: name "886-IINDPM ~", correct?

    Best regards,

    Satoshi

  • 0 in reply to Satoshi
    TI__Guru**** 165886 points

    Hi Satoshi-san,

    Regarding 1, yes. 

    Regarding 2, I interpreted VBUS->battery to be either VBUS powered up to supply system or device entering supplement mode. For Battery->VBUS, I interpreted as VBUS power down or existing supplement mode.  The load transient shows supplement mode.

    Regards,

    Jeff