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UCC21520: Peak Current Maximum Value

Shinichi Inoue
Guru 21741 points
Part Number: UCC21520

Dear Specialists,

My customer is considering changing UCC21520 and has questions.

I would be grateful if you could advise.

---

UCC21520 peak output source/sink current is from datasheet page 8 OUTPUT


Peak output source current 4Atyp
Peak output sink current 6Atyp

(1) I understand that this current value is described as the peak current rating of the gate driver, is it correct?

If so, could you please let us know the MAX value of peak source/sink current. 

(2) In the UCC21520, is there a function of limiting these peak currents? .

---

I appreciate your great help in advance.

Best regards,

Shinichi

  • 0
    TI__Expert 6730 points

    Hi Shinichi, 

    Happy New Year! One of our experts will be back in office after the holidays and answer your questions. Thank you! 

    Best, 

    Vivian

  • +1 in reply to Vivian Qi
    TI__Expert 5921 points

    Hi Shinichi,

    Thanks for your patience!

    To answer the questions:

    Shinichi Inoue said:
    (1) I understand that this current value is described as the peak current rating of the gate driver, is it correct?

    I believe this app note does a better job answering this question than I can in a short post: https://www.ti.com/lit/an/slla387a/slla387a.pdf

    To summarize, this is correct, the rated current is the measured peak during testing at the specified conditions.

    The actual value will depend heavily on external gate resistance and even the elad resistance of the power switch.

    Shinichi Inoue said:
    (2) In the UCC21520, is there a function of limiting these peak currents? .

    This driver does not have an internal function to limit this peak current. If the peak current needs to be limited an external gate resistor should be used such that (VDD-VSS)/Rgate < Max allowable current in the application. See the app note  linked above for more detailed equations.

    If this answers your questions please click the green button, otherwise please let us know how we can help further.

    Regards,

    Daniel

  • 0 in reply to Daniel Norwood
    Guru 21741 points

    Hi Daniel,

    Thank you for your reply.

    I'll share your answer with the customer.

    And I have an additional question, could you please advise.

    Regarding Peak output source current(4A) and Peak output sink current(6A) are only specified typical value.

    Could you please let us know maximum/minimum value?

    How much deviation should we expect, +/-20% or +/-30%?

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

  • +1 in reply to Shinichi Inoue
    TI__Expert 5921 points

    Hi Schinichi,

    In the actual customer application the peak drive strength is generally controlled by the gate resistance. For example, if a VDD of 12V is used with a 4 Ohm total gate resistance the peak current would be limited to about 3A, but if the total gate resistance is 6 Ohm the peak current would only be about 2A.

    This means that the relatively small variance in peak output current of the device on it's own have little impact. This is especially true since the customer scenario will likely not match the test conditions of the datasheet:

    Do you know why this information is needed?

    Regards,

    Daniel

  • 0 in reply to Daniel Norwood
    Guru 21741 points

    Hi Daniel,

    Thank you for your reply.

    I shared your suggestion with the customer and they understood. 

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi