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BQ25798: Application question

Alice Fan
Intellectual 2280 points
Part Number: BQ25798


Tool/software:

Hi team,

Our customers have several application questions.
(1) Since there is external CC logic, BQ is not required for BC1.2 judgment. Since D+/D- are not used, do they need pull-down, pull-up, or N.C.?
(2) When should VBUS, ACDRV1 & ACDRV2 be used?
(3) As shown in the figure below, can the initial setting for 2S to VSYSMIN 6V be changed?
(4) When should the red box "Optional" be used?

Thanks!

Best,

Alice

  • 0
    TI__Guru**** 167726 points

    Hi Alice,

    Regarding 1, NC.

    Regarding 2, VBUS is input power to the charger.  ACDRVx drive external back to back MUX FETs to allow for different inputs.  The output side of the MUX FETs connect to VBUS.

    Regarding 3, after the host processor comes up, the host can write to change of the PROG pin default values.  The PROG pin default values per resistor setting cannot be changed.  MINSYS must be set less than VREG.

    Regarding 4, the internal BATFET between SYS and BAT always has the body diode that allows current flow from battery to SYS load.  If the application requires a "ship mode" where the system is off and the charger is in lowest battery Iq state, the charger's SDRV pin can drive the gate of an external shipFET to completely disconnect the battery from the system load.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    TI__Intellectual 2280 points

    Hi Jeff,

    Thanks for your reply.

    What’s the Iq for REGN LDO ?

    If Iq is out of my expectation, Can I turn it OFF for power-saving?

    If not, how can we reduce the Iq of REGN LDO?

    Thanks!

    Best,

    Alice

  • 0 in reply to Alice Fan
    TI__Guru**** 167726 points

    Hi Alice,

    We do not have Iq for REGN broken out from the rest of the charger.  REGN output is only available when valid VBUS voltage is applied. If VBUS is applied, the charger can be forced into high impedance (HiZ) mode (similar to when no VBUS is applied) by setting EN_HIZ bit =1 but that also turns off the converter and turns on the BATFET so that SYS=BAT.

    Regards,

    Jeff