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BQ25619: Over current protection in Buck converter part

Part Number: BQ25619

Hello team,

My customer has a question about overcurrent protection of BQ25619.

He understood from the datasheet that IINDPM can be used for overcurrent protection.
But he is concerned with BQ25619 behavior of Buck converter part when the load connected to the VSYS pin is shorted.
Besides IINDPM and VINDPM, is there any overcurrent detection in the buck converter part (HSFET(Q2) LSFET(Q3))?
What happens to BQ25619 if the load connected to the VSYS pin is shorted when DC power supply come from VBUS pin.

Your advice is appreciated.

Best Regards,
Akihisa Tamazaki

  • Hi Akihisa,

    Please see Section 8.3.2 with regards to I_SYS_OCP_Q4. "When the system is overloaded or shorted (IBAT > ISYS_OCP_Q4), the device turns off BATFET immediately."

    Regards,

    Mike Emanuel

  • Mike-san,

    Thank you for your comment.
    I am sorry for not being able to inform you the intent of the question of the customer. Let me confirm the device behavior when sys is overloaded.

    The power supply to the sys come from VBUS and from the battery as the red and blue arrows in the following figure. Please consider when sys is overloaded in this state.

    When the battery is powered (blue), as you have pointed out, the device monitors I_SYS_OCP_Q4 and protects the over current.
    When VBUS  is powered(red), the device seems to monitor IINDPM and protected, do not monitor at the HSFET(Q2) or LSFET(Q3) as far as I saw the datasheet,
    If sys is overloaded, it is expected that the device will enter shipping mode, and in some cases the current protection will work by IINDPM, then PMID output will disappear.

    I am considering above. Is it correct?

    Your advice is appreciated.

    Best Regards,
    Akihisa Tamazaki


  • Akihisa-san,

    If the converter is in IINDPM, the PMID voltage will not disappear as the input current will be regulated.

    Regards,

    Mike Emanuel

  • Mike-san,

    I understood. The customer also understood it.
    Thank you for your support.

    Best Regards,
    Akihisa Tamazaki