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BQ24266: Output reset

user5006944
Intellectual 630 points
Part Number: BQ24266


BQ24266 will be connected in parallel DCDC for the system power supply, when there is no battery when the power supply instantly, Vsys voltage will drop from 4.5 to 2.6, which lead to  the system restart.When I give a CAP of  100μF on Vsys,that is ok .But I can not give a big CAP in my application.Is there anther way?

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    TI__Guru**** 170496 points

    When in constant voltage mode (battery absent or fully charged), the bq24266 is trying to regulate SYS to a fixed voltage. It is not designed to handle a parallel power supply attached to SYS.  I suspect that your power supply is overshooting slightly (something the additional capacitance eliminates), which causes the bq24266 to think there is an over-voltage condition.  If your application requires the parallel power supply, then I suggest adding a Schottky diode (or ideal diode created by LM5050 and external PFET) from SYS to the output of the additional power supply.  When no battery is attached, there is little risk to the bq24266 but when a battery is attached, the battery could see unregulated charge current from this supply.