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LMG5200EVM-01A: Use as a 7MHz Class D amp

Adam Tetreau
Prodigy 25 points

Part Number: LMG5200EVM-01A

My team needs an amplifier capable of 50V (1A max) @ 7MHz to provide wireless power/data through resonant coupled coils.  We liked the look of your LMG5200 and bought a handful of the LMG5200EVM-01A eval boards.  By bypassing the inductor and removing the capacitors at the SW output we had what seemed like a workable Class D amplifier.  These modified boards were providing plenty of power and producing a useful signal over the coils (despite what looks like some 100MHz noise) but a few of them have failed after moderate use.

It is unclear to us whether these failures are due to something like racethrough current, or if we are just outside the operating frequency.  A search through the Community forums suggests that these boards are rated for 5MHz, but that they should be able to operate at a higher frequency than that.

So my real question is: does TI have a better product for our requirements than the LMG5200?  

Thanks in advance.

Adam

  • 0
    TI__Intellectual 2910 points
    Adam,

    Thanks for evaluating the LMG5200EVM-01A for your application. I regret hearing that some parts have failed when running above the 5MHz rating.

    The main concern at higher frequencies is thermal management. Although the gate driver in the LMG5200 is capable of, for example, 7MHz, careful consideration must be applied to heat-sinking and other cooling (such as airflow) in order to ensure that the maximum operating junction temperature of 125ºC is not exceeded. Have you been using external cooling during your tests?

    Regarding other products available, one approach would be to design using LM5113 GaN gate driver along with GaN FETs for the half-bridge. Note that this approach does not have the advantage of the simplified layout and single-device solution offered by the LMG5200.

    Regards,

    - Daniel
  • 0 in reply to Daniel Ruiz
    Prodigy 25 points

    Daniel,

    We were not using any external cooling, so I think you've identified the most likely culprit.

    We will take a look at the LM5113.

    Thanks for the response.

    Adam