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BQ25895: Thermal Calculations

Mitchell
Expert 4915 points
Part Number: BQ25895

Hi Team,

My customer is trying to calculate the power dissipation (Pd) of the BQ25895. We're not seeing any calculations other than the theta information in the spec, the spreadsheet tool or WEBENCH.  Do you have a tool to calculate thermal dissipation for this part?

Thanks,
Mitchell

  • 0
    TI__Guru**** 166826 points

    Hi Mitchell,

    Unfortunately no.  The thermal calculator at and explained in the app note:    is no longer functioning.  I have submitted a ticket to determine its fate.

    Regardless, powerpad IC power dissipation is a function of PCB construction and board layout and proximity to other ICs that use the same copper area for heat sinking (i.e. thermally saturated copper are).  You can use RthetaJA to get a rough IC package temp rise estimate but it assumes a very specific PCB type and area and assumes copper that has infinite heat sinking.  The best solution is to use thermal simulation software with the psi values instead of theta values. If simulation software is not available, then I suggest taking real thermal data, starting with the EVM. 

    We have some EVM thermal data for specific configurations.  What is your customer's input voltage, charge current and fully charged battery voltage?

    Regards,

    Jeff

     

  • 0 in reply to Jeff F
    TI__Guru**** 166826 points

    Hi Mitchell,

    The pcb thermal calculator on the TI website mentioned above is working.  You have to start typing a part number.  The BQ parts are not there but if you find a QFN part that has a similar RthetaJB, you can get an idea of the copper area needed to dissipate the heat (assuming no airflow and no other IC's using the same copper for heat sinking).

    Regards,

    Jeff