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Original question:

LMG1020: About LMG1020 output

LMG1020: Drivering the MOSFET

suy
Expert 1055 points
Part Number: LMG1020

Hi,

   I want to use the 1020 drivering the power MOSFET，can you confirm that for me whether the mos driver can drive the accessory MOSFET ？

   Just only i calculate the driver current？（1020 driver current > I=Qg/Tr+Ton ）

   2021.ONSM-S-A0001842162-1.pdf 

  

  • 0
    TI__Genius 12990 points

    Hi Suy,

    Thanks for reaching out on lmg1020.

    1020 can be used to drive a MOSFET or GaN FET. It is capable of 7A peak source current for 350ps of rise time and 5A peak sick current for similarly fast fall time.

    The average gate drive current to switch the gate is Ig(avg) = Qg x Fsw

    Let me know if this helps answer your question or you have any other questions.

    Thanks,

  • 0 in reply to Jeffrey Mueller
    Expert 1055 points

    Hi jeff,

       Thanks for your answer.

       I noticed the average current you mentioned，but the1020 gives the peak current，how do i konw the average current of the 1020.

       For in the accessory MOSFET，if working on 1MHz,Vgs = 5V, Ig = 90nC * 1MHz = 90mA，if i want to use 1020 drive this MOS，i must set the duty cycle less than 0.013（DC≤ 90mA / 7A = 0.013），am i right？

  • 0 in reply to suy
    TI__Genius 12990 points

    Thanks for the update Suy,

    You would need to measure the peak current of 1020 to calculate the average current (which should be similar to the Ig calculation in the last post.

    Once the gate is charged up, no gate drive current is needed othr than leakage to keep the gate charged.

    The max duty cycle depends also on VDD capacitance value and gate leakage. If no gate to source resistor is there and minimal leakage happens then well over 50% duty cycle could be possible. Make sure there is enough 1020 VDD capacitance for your system to keep the gate charged.

    Does this help you answer your question?

    Please let me know if you have any other questions.

    Thanks,

  • 0 in reply to Jeffrey Mueller
    Expert 1055 points

    Hi jeff，

      I'm sorry that i still can't understand what you mean.

      Your first reply said that i can confirm whether the 1020 can drive the MOSFET by calculating the average current, but the 1020 only gives the instantaneous current. You do not need to know the average current output by the 1020 to judge whether it can drive the MOSFET?  Or is the average current required by the MOSFET to infer the current provided by the MOS DRIVER, is my calculation method correct?

    Thank you！

  • 0 in reply to suy
    TI__Genius 12990 points

    Hi Suy, thanks for your update.

    You need to know average current to stay under the junction temperature. However this is a function of the pcb and 1020 package dissipation.

    1020 uses the peak current to achieve fast rise time with the calculation tr = Qg / Ipeak

    Your calculation method is correct for average current however the duty cycle will depend on many factors.

    Thanks,

  • 0 in reply to Jeffrey Mueller
    Expert 1055 points

    Jeff，

       I understand now, thank you very much