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UCC27611: Low pulldown impedance against Miller turnon

Koshi Ninomiya
Expert 5435 points
Part Number: UCC27611

Hi Team,

My customer is evaluating the UCC27611 by UCC27611OLEVM-203 to drive GaN FET EPC2022. They were advised by EPC that  external gate resistance was recommended to be 0 ohm. Under this condition, pulldown impedance is only 0.35 ohm of the UCC27611. On the other hand, absolute maximum rating of sink current (0.5us) of the UCC27611 is 6A (max). Then, they are worried that the peak value of the sink current may exceed the rated value of 6A when turnoff. 
How should we consider the sink current peak value when turnoff?
Please advise the criteria the sink current peak value when turnoff.
Thank you.

Best Regards,

Koshi Ninomiya

  • 0
    TI__Genius 13445 points

    Hello Koshi,

    Thanks for reaching out.

    Please refer to the attached link source/sink current considerations.

    https://www.ti.com/lit/an/slla387a/slla387a.pdf

    Regards,

    -Mamadou

  • 0 in reply to Mamadou Diallo
    TI__Expert 5435 points

    Hi Mamadou-san,

    I looked at Tech Note of "Understanding Peak Source and Sink Current Parameters" slla387.
    There is the Equation 2 for IOL calculation.
    In case of the UCC27611, what is RGFET_int value?
    The absolute maximum rating of sink current is 6A, dose the UCC27611 have output current limit function?
    Otherwise, we can not use the equation of IOL=min(6A, VREF/(ROL+ROFF+RGFET_Int)).

    The customer is worried that the peak value of the sink current may exceed the absolute maximum rating of 6A under ROFF=0ohm when turnoff. 
    Thank you.

    Best Regards,

    Koshi Ninomiya

  • 0
    TI__Genius 12990 points

    Hi Koshi,

    Thanks for reaching out on ucc27611. The sink and source peak current of the gate driver,  guaranteed by the datasheet, is limited internally so that the current will not reach above a max of 6A for sink current. using 0ohm gate resistor should not be a problem since the EPC is a small gate charge the full sink current pulse of <10ns should discharge the gate rather than the full 0.5us pulse. Let me know if this helps answer your question or you have any other questions.

    Thanks,