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LMG3622: GaN Normally off

Shuji Ishiwata
Mastermind 8210 points

Part Number: LMG3622

Hi All,

I have a question regarding TI's GaN products.
It says that normally off is possible in product web page, but are there any documents?
https://www.ti.com/power-management/power-stages/gallium-nitride-power-stages/overview.html 

I would like to know how they achieve normally off.

Best Regards,
Ishiwata

  • 0
    TI__Expert 8145 points

    Hi Ishitawa-san,

    Our GaN portfolio consists of both enhancement mode and depletion mode devices. An enhancement mode device is normally-off while a depletion mode device is normally-on. 

    To make d-mode devices behave as normally-off devices, we implement a Silcon FET in series with the GaN FET, but drive the gate of the GaN FET directly. This is known as direct-drive. The white paper that you highlighted above provides more information on this technology. Please feel free to read through it to understand this mechanism. 

    Best Regards,

    John 

  • 0 in reply to John Gomez
    Mastermind 8210 points

    Hello John-san,


    Thank you for your answer.

    Sorry about the late reply.

    I may not understand it yet.

    Is the following understanding correct?
    ・TI products have both enhancement mode and depletion mode devices.
    ・Enhancement mode products are normally off.
    ・Depression mode products are normally on.
    ・Depression mode products need to implement Silcon FET in series

    For example, is LMG3622 in enhancement mode or depletion mode?


    Best Regards,
    Ishiwata

  • 0 in reply to Shuji Ishiwata
    TI__Expert 8145 points

    Hi Ishitawa-san, 

    Yes, your statements are correct. LMG3622 is an enhancement mode FET. 

    Best Regards,

    John

  • 0 in reply to John Gomez
    Mastermind 8210 points

    Hello John-san,

    Thank you for your answer.

    Where can I tell that it is an enhanced mode FET in the LMG3622 data sheet?

    Best Regards,
    Ishiwata

  • +1 in reply to Shuji Ishiwata
    TI__Expert 8145 points

    Hi Ishiwata-san, 

    Our datasheets don't mention whether they are e-mode or d-mode. However, our d-mode devices (LMG342x, LMG352x, LMG341x) require an external buck-boost inductor for their internal inverting buck-boost regulator. This regulator provides a negative voltage to turn off the GaN FET. This is one way to tell if the device is d-mode. 

    Best Regards,

    John