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Original question:

LM5156: Can boost controller, LM5156 and LM5122 drive GaNFET?

LM5122: Driving GaN FET

Nuno Martins
Prodigy 40 points
Part Number: LM5122

Tool/software:

 Is LM5122 able to drive GaN FETs?

I saw some related topics where was said that LM5122 was not able to drive GaN FETs.

What is the reason? Now they can be driven with 0V and 5V, like a silicon FET.

  • 0
    TI__Guru 65580 points

    Hello Nuno Martins,

    LM5122 drivers have a high voltage of roughly 7.5V. So the voltage level on the gate is too high for the GaNs I know.

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Prodigy 40 points

    Hello Brigitte,

    About the VCC regulator, in the datasheet says:

    "When the input voltage is below the VCC setpoint level, the VCC output tracks VIN with a small dropout voltage."

    It says also it can be powered from an external supply, so we could connect both VIN and VCC to 5V, for example.

    There's anything else that may not make it compatible with GaN?

    Best regards,

    Nuno

  • 0 in reply to Nuno Martins
    TI__Guru 65580 points

    Hello Nuno,

    In general this sounds reasonable. We did not test it this way and although I do not expect anything speaking against it, I can not guarantee that it will work.

    The device is not optimized for such a low supply voltage, so some of the parameters might look different.

    The dead time is not optimized for GaN and might be a little long, so you might want to have a diode in parallel to the gate for reducing losses.

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Prodigy 40 points

    Hello Brigitte,

    Thank you. Could you please suggest a suitable part compatible with GaN?

    Best regards,

    Nuno

  • 0 in reply to Nuno Martins
    TI__Mastermind 30280 points

    Hi Nuno,

    Unfortunately, we do not have a GaN driver controller with the same specs as LM5122 within our portfolio yet. (With new product development, this may change in the future)
    For now, do you have the specs for your application? Vin voltage range, Vout voltage, max load conditions?
    Based on this, we may find a suitable part within in full TI portfolio.

    Best regards,
    Niklas

  • 0 in reply to Niklas Schwarz
    Prodigy 40 points

    Hi Niklas,

    For this application we need a Boost converter with high efficiency for minimum input voltage 8V, output voltage 40V and power 300W.

    What would be your suggestion?

    Best regards,

    Nuno

  • 0 in reply to Nuno Martins
    TI__Mastermind 30280 points

    Hello Nuno,

    Thanks for the feedback.
    I got some additional feedback from within our team on suitable device.
    It turns out LM5122 is generally not suited for GaN applications. Even if BIAS and VCC are supplied externally with 5V, the internal deadtimes of LM5122 are not ideal for GaN FETs.

    I checked for other solutions that also include external GaN drivers LMG2100 or LMG3100, but these do not work with our controllers either.

    For a 300W application, it should be possible to reach high efficiency with a regular non-GaN application using LM5123 as well.
    If GaN driver are essential for the application, we do not have any suitable parts at the moment.

    Best regards,
    Niklas