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Backup battery charging

Antony Lin
Genius 13480 points
Other Parts Discussed in Thread: TPS65950

We wish to keep backup battery charging enabled during WAITON state, but not sure the behavior of BBCHEN bit.

In the "Description" of BB_CFG register, it's in VRRTC domain.  -> I assume the whole register value will be kept if VRRTC is valid.

But in the description of  BBCHEN bit, it's said "Reset when signal triton_reset_na is low (WAITON state)."  Does it mean this bit will be reset (to 0) when the chip enters WAITON state?  If so, does it mean it's impossible to charge backup battery when the chip is in WAITON state?

Thanks.

Antony

  • 0
    Prodigy 245 points

    This is something I'd been intending to ask too - as well as :

    • If it's expected that our backup battery (well, super-cap) ends up charged to 3.3v when the charge voltage is set at 3.2v in BBSEL.
    • Why our backup battery discharge rate seems to be 6.8 - 7.0 uA rather than the 2.25 uA indicated in the TPS65950 data manual.

    However I think this really needs to be posted in the power management IC forum (I'll do so!)

    ~Pev

  • 0 in reply to Pev
    TI__Genius 15100 points

    Antony,

    You are right. BB_CFG value will reset.

    Only those registers retain value which are mentioned as (backup domain). BB_CFG is not part of this.

     

    Regards,

    Gandhar.

     

  • 0 in reply to Gandhar Dighe
    TI__Genius 13480 points

    Hi Gandhar,

     

    My understanding is,

    [VRRTC domain] registers means the register values will be kept if VRRTC is valid.  (Regarding VRRTC, is it available during WAITON mode? e.g. VBAT>3.2V )

    [Backup domain] registers means the register values will be kept if there is valid BKBAT or VBAT.

    Am I right?

     

    Since BB_CFG  will be reset during WAITON mode, that means it's impossible to charge the backup battery from VBAT during WAITON mode even when VBAT>3.2v?

    Thanks,

    Antony