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LMG5200: External 5V for upper device instead of bootstrap supply

Steven Hansen
Intellectual 666 points
Part Number: LMG5200

Tool/software:

We are considering using LMG5200 as a gate driver stage for driving parallel GaN devices (hence requiring significant gate current).

I'm wondering if it's possible to bypass the internal bootstrap supply for the LMG5200 upper device and bring a floating 5V bias supply into pin HB instead? This gives us a larger duty cycle range and allows single pulses to propagate (impossible with a bootstrap supply).

If the external voltage is tightly regulated to 5V, would we need to worry about the overvoltage clamp?

  • 0
    TI__Expert 7435 points

    Hey Steven,

    Yes, you can power the high side of the LMG5200 with a 5V isolated bias supply connected to HB-HS. The clamp voltage is at 5V typ. so it will protect the GaN FET gate from overvoltage.

    There are also LMG2100R044 & LMG2100R026 for higher current application. These are 4.4 and 2.6mohm 100V half-bridges with integrated gate driver similar to the LMG5200.

    Best,

    Kyle Wolf

  • 0 in reply to Kyle Wolf
    Intellectual 666 points

    Hi Kyle, can you share any info about how the clamp works? I see the datasheet calls out a clamp regulation voltage of 4.65V to 5.2V.

    I'm not 100% sure how to interpret this. Could the clamp activate if the external supply is at 5V (above 4.65V)? Or can I avoid the clamp by regulating the external supply so it's always above 4.65V and below 5.2V?

  • 0 in reply to Steven Hansen
    TI__Expert 7435 points

    Hey Steven,

    I talked with the designer and it isn't really a voltage clamp, there is a FET in series with the bootstrap diode that turns off when the bootstrap cap's voltage is above the 5V typ.

    Best,

    Kyle