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UCC27322-Q1: UCC27322-Q1 Power dissipation calculate question

Chao Fu Chen
Intellectual 1050 points
Part Number: UCC27322-Q1
Other Parts Discussed in Thread: UCC27322

Hi Team,

My customer mentioned the power dissipation issue when he use the UCC27322 to driver 3 mosfet.

And he follow our power dissipation formula to see the P =  Qg x V x F.

This Qg need the use the 3 times cause he has 3 mosfet to trigger that  or just 1 is enough ?

Eddie

  • 0
    TI__Mastermind 21575 points

    Hello Eddie,

    For calculating the power dissipation, you should use the total Qg of all 3 Mosfets in parallel for the calculation. Confirm if this addresses your question.

    Regards,

  • 0 in reply to Richard Herring
    TI__Intellectual 1050 points

    Hi Richard,

    As you mentioned, the 3 mosfet is parallel. So his Qg is plus the 3 times.

    And the answer is P = 3Qg x V x F. Am i right ?

    But for their calculate the P is 0.67W

    TJ = TC + 0.67 X 45.3C/WRθJC(top)

    Their TC measurement is 116 degree.

    SO his TJ is too much higher to 146.3 degree.

    Is it truth ? Or any calculate formula and parameter is wrong in here ?

    Because his end customer ask them the TJ have to under the spec 10 degree.

    It is confuse and hard for them to do form this calculate result.

    Please help to check. Thanks!  

  • +1 in reply to Chao Fu Chen
    TI__Expert 4070 points

    Hi Eddie,

    For a more in-depth calculation on thermal calculations, please see this application note.  This should get you closer.

    Please let me know if that application not helps answer your question.

    --------

    Yes, as you did, you must multiply the gate charge by 3 to accurately calculate the power.

    --------

    Thanks,

    Aaron Grgurich