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LMG1210: Regarding external SBD

Taroimo
Intellectual 680 points
Part Number: LMG1210

Tool/software:

Dear TI team

 

We are considering using the LMG1210 to drive a GaNFET.

A gate resistor has been inserted between the gate driver output and the gate pin of the GaNFET to reduce overshoot/undershoot caused by parasitic inductance.

In addition, an SBD has been inserted in parallel with the gate resistor to improve turn-off speed.

 

The datasheet states that the maximum peak sink current of the LMG1210 is 4.3A.

 

To make full use of this performance, I believe the SBD should have an IFSM (Peak Surge Forward Current) of 4.3A or more.

Is this understanding correct?

 

Best Regards,

Taroimo

  • 0
    TI__Intellectual 1340 points

    Hi Taroimo,

    Thanks for reaching out to TI.

    What we'd recommend here is a diode voltage equal to or greater than the FETs. Typically, didoes of half-bridges tend to be rated about between 1-2A with a surge rating much higher than that. The diode can see peak surges during discharging and charging of the capacitor, so we'd recommend to use a diode with a surge rating higher than the peak current of the half-bridge.

    Best,

    Jeremiah

  • 0 in reply to Jeremiah Vo
    Intellectual 680 points

    Hi Jeremiah,

     

    I'm sorry, but I haven't been able to communicate my concerns very well, so I'll change my question.

    The LMG1210 evaluation board has 0 Ω inserted between the gate driver output and the gate pin of the GaNFET

    so there is no gate resistor, so I understand that the transient current at turn-on/turn-off will be very large.

     

    The electrical characteristics of the LMG1210 below list Iol/Ioh,

    but does this mean that the values ​​in the table below can be kept by the resistors inside the gate driver without the need for external resistors?

    Or should I design it so that I can keep it below the minimum value in the table by inserting an appropriate gate resistor value?

     

     

    Best Regards,

    Taroimo

  • +1 in reply to Taroimo
    TI__Intellectual 1340 points

    Hi Taroimo,

    You would be correct, the internals of the gate driver will maintain the values in the table you provided assuming operating within recommended conditions.

    A gate resistor of even 0 ohms is still recommended to have, as it limits current which in turn limits overshoot or undershoot.

    Thanks,

    Jeremiah