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BQ24133: BQ24133 charging abnormal

Part Number: BQ24133

Hi 

The customer design with BQ24133 to charge 3 series battery, and the charging current is 1.2A.

A switch is added to the PVCC output to disconnect or connect the subsequent circuit. If they don't turn on the switch, charging is normal, but once they turn on the switch, it won't charge and the LED blinking.

If they turn on the switch and then connect the adapter, they can charge normally. When the power switch is turned on, the adapter voltage will be pulled down for a moment, but it will recover immediately, about 100us.

After raising the adapter voltage from 15V to 16.5V, this problem still occurs.

Attached the schematic 

The adapter voltage pulled down about 100us, when the switch is turned on, the capacitor on the downstream circuit is charged, and the instantaneous current is large, so there will be a 100us voltage drop.

 When the switch turn on, why it can't charge and the LED blinking?

Please help check it.

Thanks

Star

  • HI Star,

    The schematic is missing some capacitors:

    Also, how is AVCC connected?  The fault is one of the below:

    If still an issue after the capacitors above are added, Can you get an oscope shot of 15Vin, PVCC and BAT?

    Regards,

    Jeff