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BQ24650 Behavioral Questions

Amanda Ross95
Intellectual 2740 points
Other Parts Discussed in Thread: BQ24650

Hello,

I have a couple questions regarding the behavior of the BQ24650 under certain circumstances:

1.) Given a Vin = 18V and a Tj in the range of 25 to 100 deg Celcius, What is the maximum power the internal MOSFET driver can withstand?

2.) If Vin is present and MPPT set is >1.2V, if the battery becomes disconnected, what voltage should show on the output?

3.) If Vin is present and MPPT set is equal to 0V, if the battery becomes disconnected, what voltage should show on the output?

I appreciate any feedback you can give.

Thanks so much for your time!

-Amanda

  • 0
    TI__Genius 11480 points

    Hi Amanda,

    1) Hm, this is a good question. I will try to find more info about the gate driver specifically - that is something I have never looked into. I will find out more and reply to your post again. However, you can find an "upper limit" so to speak by using the max power of the IC and working backwards. If there is a temperature rise of 100C (from the IC only) from junction to ambient - the IC will dissipate about 2.25 W. Some fraction of that will be used by the gate drivers.

    What are you trying to accomplish? I may be able to find more info if I know more about what you are trying to do. I would be surprised if the gate drivers fail from dissipating too much power.

    2) Are you following the EVM schematic and taking Vsys as your output, or are you just considering Vbat your output?

    If you are following the EVM, Vsys will be ~Vadapter with no battery,

    If you are looking for Vbat, the voltage will be your regulation voltage and the IC will run the battery detection routine. The voltage will still be Vbat because the buck converter is still running.

    3) If you disable charge by setting VMPPSET and remove the battery, Vbat will be ~0. This is because you stop the converter from switching. If you are following the EVM, Vsys will still be ~Vadapter.

  • 0 in reply to David Wiest Jr
    TI__Intellectual 2740 points
    Thank you for your answer David!