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LMG1020: Develop

samba wang
Prodigy 80 points
Part Number: LMG1020

Dear All

When I reading the article "using the LMG1020-EVM Nano-second LiDAR EVM", the sentences as below can not be understood . Could anyone can helpt to describe in detail ?

The expected resonant frequency for the gate loop is ~70-90MHz (given Gate capacitance of
~10nF and Gate inductance of 3-5nH), the oscillation observed is at 250MHz, which would imply a gate
loop inductance of ~40pH. This is therefore pickup noise.

  • 0
    TI__Intellectual 2805 points

    Hello Samba, 

    Take a look at our TI Tech Note: It describes the resonant circuits in gate drive loops and helps you calculate the external gate resistance required to suppress oscillations. 

    Let me know if you have any questions! 

    If this answered your question, please press the green resolved button. 

    Regards,
    Mateo

  • 0 in reply to Mateo Begue
    Prodigy 80 points
    Hi Mateo,

    Thanks for your help . And another question , we found that PGND and GND tied on the pin GaN transistor . Could you help to explain why to do this ?

    Thanks!
  • 0 in reply to samba wang
    TI__Genius 12990 points
    Hi Samba,

    PGND and GND (kelvin GND) are pinned out separately as seen in the EVM users guide page6.

    Also check out section2 from the following IGBT app note (however it still applies to GAN):
    www.ti.com/.../slua169a.pdf

    It explains how a kelvin connection can help with common source inductance experienced at the source of the FET and the return of the gate loop. The kelvin connection taps off the source for the gate driver leaving the power train current through the channel substrate.

    does this make sense, let me know if you have any more questions.
    thanks,