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LMG3100R017: Dead-time in half-bridge configuration

Brian Gosselin
Expert 4745 points
Part Number: LMG3100R017
Other Parts Discussed in Thread: LMG3100R044,

Tool/software:

Hi Team,

This question applies to both LMG3100R017 and LMG3100R044.

I see in the datasheet, there's a note that says that "in order to allow flexibility to optimize dead-time according to design needs, the LMG3100 does not implement an overlap protection functionality."  Also, that "careful consideration must be applied to the control inputs in order to avoid a shoot-through condition."

Do you have any guidance on what would be a good dead-time for using the LMG3100 in a half-bridge configuration?  It seems <100ns is still causing some shoot-through, so looking to see what y'all would recommend.  Thanks in advance for your support.

Best Regards,
Brian

  • 0
    TI__Expert 4510 points

    Hello Brian,

    In some GaN devices, we incorporate shoot-through protection or latched input signals preventing both from turning on. However with LMG3100 we do not implement these features to allow more flexibility with deadtime.
    For example, when configuring LMG3100 in half-bridge configuration, customer can use integrated level-shifting to supply both HI and LI signals from low side device as shown:

    In this configuration, the propagation delay for HI will be significantly longer than LI since the signal needs to pass through low side device with level-shifting:

    This means that negative deadtime from PWM signal is achievable, because propagation mismatch is high. The FETs won't actually turn on together but the signal from controller will need to account for this. One way is to shift the low side signal about ~30ns later by adding RC time constant to account for the additional delay in HI signal path

    Deadtime smaller than 100ns is very achievable with LMG3100, we typically recommend at least 8-10ns of deadtime. I recommend checking the signal at low and high side device LI pin to ensure the deadtime is being applied as expected.

    Thanks,
    Zach S