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BQ24170 Themal regulation

Keiichi Kajino
Expert 2365 points

Hi folks,

If accidentary short occurs in RSR register, is the thermal regulation still available?

If no current limit at battery side and based upon HSFET RDSON and HS cycle by cycle current limit,

I guess TJ will exceed 120degC.

In this case I would like to know the thermal regulation is still avaibale or not.

  • 0
    TI__Expert 3160 points

    Keiichi

    The thermal regulation and shut down loop if available regardless of other conditions. From the datasheet:

    The internal thermal regulation loop will fold back the charge current to keep the junction temperature from exceeding 120°C. As added level of protection, the charger converter turns off and self-protects whenever the junction temperature exceeds the TSHUT threshold of 150°C. The charger stays off until the junction temperature falls below 130°C.

    Thermal regulation relies on the ability of the IC to reduce charge current and with no feedback on Rsr I'm not sure how the device would behave, but thermal shutdown will disable charge if the junction temperature exceeds 150degC to provide a safety backup. After the temperature has reduced to 130degC the device can return to charging. 

    A short across SRP/SRN will also trigger the undercurrent protection keeping the HSFET on except for when the boostrap cap drops below 4V, then the LSFET will be turned on to recharge it. The HSFET over-current protection will also be monitoring the current through the HSFET with a cycle-by-cycle limit of 8A min.

    Thanks,

    Rachel 

  • 0 in reply to Rachel Moore
    Expert 2365 points
    Rachel,
    Thank you for your reply on my question even if in case of irregular behavior.
    Our customer is now in UL recolonization test, so trying severe conditions.