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BQ25798: bq25798 does not use battery

Yaoyi Chang
Prodigy 20 points
Part Number: BQ25798

Tool/software:

Hi Ti team,

The BQ25798 is currently used to charge a 1P3S lithium battery from a 12V adapter and supply power to the system. We are evaluating whether we can remove the battery and use only the 12V adapter to power the system with the current design. How should the BQ25798 be configured in this case?

  • 0
    TI__Guru**** 166826 points

    Hi Yaoyi,

    The BQ25798 can be used without a battery and with charge enabled (i.e. CE pin = GND, CE bit =1 and no TS fault due to missing thermistor).  With charge enabled and only the minimum capacitance on BAT pin, the voltage at BAT will cycle between charge, OVP, termination, recharge, resulting in a triangle waveform.  The voltage on SYS follows BAT but never dips below MINSYS voltage.  With no battery connected it is recommended to disable charge with CE pin, CE bit or TS fault.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 20 points

    Hi Jeff,

    Thanks for your reply.

    One more question. Can the MINSYS voltage be increased through settings when there is no battery connected?

  • 0 in reply to Yaoyi Chang
    TI__Guru**** 166826 points

    Hi Yaohi,

    Yes but the charger does not support MINSYS > VREG.  So the host must first increase VREG and then MINSYS.  VREG and MINSYS would have to be lowered before battery re-attach.

    Regards,

    Jeff