BQ24133: Do I need to add reverse blocking diode even if the charger input is not connected to the system output?

Part Number: BQ24133

Dear Sir/Madam,

I am using BQ24133, in my previous circuit, I am not connecting the Charger input to the system output. Because of this, we did not use and ACFET and left it floating or NC.

Now I want to put in the ACFET for soft start.

Is it OK if only the ACFET is mounted or is it necessary to add a reverse blocking diode even if the charger input is not connected to the system output?

Best Regards,

KPK

  • Hello,

    The ACFET you have inserted is actually the Reverse Blocking FET. If you would like to add the ACFET for soft start a second FET will be needed. Page 29 of the datasheet shows how to configure the ACFET and the Reverse Blocking FET.

    Page 30 of the datasheet shows an example schematic where the system is not connected to the input. You do not need to connect the charger input to the system with a diode.

    Thanks,

    Mike Emanuel

    Please click "Resolved" if this answered your question.

  • Dear sir, 

    Here is the updated schematic image for the charger circuitry.

    the charger input is not connected to the SYSTEM output and we added a soft start FET for the charger IC.

    However, we found that when there is no adapter input, battery voltage can be seen through the PVCC pin.  I think it is because the battery voltage passes through the SW pin where there is an internal FET in the IC which connects it to PVCC pin via the body diode.

    To eliminate the battery voltage back flowing to the charger input we added a reverse blocking diode instead of using a FET.

    We want to check with you if there will be no issues regarding this circuit?

  • Hello,

    You can use the reverse blocking diode to prevent current from coming out of the charger.

    Thanks,

    Mike Emanuel

    Please click "Resolved" if this answered your question.