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LMG3422R050: Body Diodes needed

Hideki Hayashi1
Expert 6590 points
Part Number: LMG3422R050
Other Parts Discussed in Thread: LMG3410EVM-018

HI team,

Customer try to use GaN FET as a switching element on H bridge inverter as replacement from IGBT.

Since it is H bridge, body diode must be needed as free wheel diode. If GaN is used for such systems, it is required to place FWD externally?

Regards,

Hayashi

  • 0
    TI__Intellectual 1670 points

    Hello,

    Our devices are frequently used as synchronous rectifiers for high power applications, meaning no external diode is necessary. I would encourage your customer to look at the specific evaluation modulus for this device which utilize a half-bridge configuration to create either a synchronous buck or boost converter.

    Please let me know if you have any further questions,

    Zach

  • 0 in reply to Zachary Soviero
    TI__Expert 6590 points

    Hi Zach,

    Customer is evaluating LMG3410EVM-018. Is it what you should know?

    Sorry I had mistake on the part number of the thread.

    Regards,

    Hayashi

  • 0 in reply to Hideki Hayashi1
    TI__Intellectual 1670 points

    Hello,

    All of the things I mentioned about our LMG3422 devices also apply for the LMG3410. It can be used as a synchronous rectifier and the EVM you referenced can be configured as a synchronous buck or boost converter using the LMG34XX-BB-EVM.  

    Regards,

    Zach

  • 0 in reply to Zachary Soviero
    TI__Expert 6590 points

    HI Zach,

    Sorry I don't understand well. How does the LMG3410EVM-018 work in dead battery period?

    I understand as the current flows body diode when both FETs off. When the both FETs off, where does the charge come from?

    Best regards,

    Hayashi

  • 0 in reply to Hideki Hayashi1
    TI__Intellectual 1670 points

    Hello,

    When the LMG341x device is used as a synchronous rectifier, the operation is different than a normal diode or silicon FET. Both FETs do not turn off, rather, the bottom side FET turns ON and acts as a diode for the free-wheeling current. The current flows from source to drain through the bottom side GaN FET channel with the device on which reduces loses because the power loss on the bottom side FET in this instance is just I^2*R where R is the RDSon of the FET (very small).

    I can explain further if you need, let me know.

    Zach