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LMG1210EVM-012: Recommended GaN FETs for switching near 50MHz

Joshua Herschell
Prodigy 10 points
Part Number: LMG1210EVM-012
Other Parts Discussed in Thread: LMG1210

Tool/software:

Hello,

I am trying to drive a load as close to 50MHz as possible without any thermal throttling from the LMG1210. Using the eval board, I was able to get to about 22MHz with the stock EPC2001C FETs before it begin to thermally throttle by bypassing the LDO of the chip, but I would like to drive it even faster. I am considering the EPC2014C as a drop-in replacement for the previous FETs, since the die outline is almost identical to the EPC2001C, just without pins 6-11. Is it possible to remove the EPC2001Cs from the eval board and drop in the EPC2014Cs as a replacement to operate at higher frequencies? If so, do any other modifications need to be made, like to the bootstrap capacitor for instance?

Thank you

  • 0
    TI__Genius 9780 points

    Hello,

    The lower gate charge of EPC2014C should improve switching speed. The bootstrap capacitor should not need to be changed since the FET gate charge is smaller. Make sure not to exceed the 40V VDS rating of the EPC2014C.

    The pin width spacing is slightly different but it might fit if the new fet is centered correctly on the pads.

    Thanks,

    Walter

  • 0 in reply to Walter Zollinger
    Prodigy 10 points

    Walter,

    I dropped the new FETs in without replacing the bootstrap capacitor. During testing, I was originally seeing extremely poor performance at frequencies above 22MHz, worse even than with the EPC2001Cs in. I was supplying the input signal in PWM mode, with jumper J3 shorted and J6 open, just as they were when the board arrived. However, after switching to independent mode, all of the performance problems I was seeing disappeared, and the board seems to have no thermal throttling or issues driving the FETs even at near 50MHz. 

    For the sake of reducing design complexity, it is greatly desirable to use the LMG1210 in PWM mode rather than independent. Do you have any insight into the difference in performance between the two modes of operation and whether PWM could be improved?

    Thank you,
    Joshua Herschell

  • 0 in reply to Joshua Herschell
    TI__Genius 9780 points

    Hello Joshua,

    Based on the deadtime setting in PWM mode, it might be limiting the max switching speed. Have you adjusted the dead time adjustment potentiometers to set the minimum deadtime without shoot through when using PWM mode?

    Thanks,

    Walter