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LMG1205: Propagation delay matching

Kaiyu Wang
Prodigy 30 points
Part Number: LMG1205

Hello. I have a general question about the LMG1205 propagation delay matching. The data sheet specifies the typical value and max value, but it doesn't specify the min value.

In another words, if our input signal has a deadtime of 3ns, will this deadtime be eaten up by the gate drive and cause the system shoot-though? Will the gate driver guarantee the delay match only be positive number, which means the rising edge always has longer delay than the falling edge?

Thanks,

Kaiyu

  • 0
    TI__Genius 9865 points

    Hey Kaiyu,

    Thank you for your question.

    For delay matching, the 3ns of deadtime is not taken up by the gate driver. If the signal is simultaneously applied at the inputs of two channels, the time delay difference at the outputs is the delay matching specification. The lower the spec of delay matching, the lower the risk of shoot through. Delay matching is what tells you how well the internal propagation delays between channels are matched.

    But, 3ns of deadtime on the inputs is very aggressive and you could see issues due to the parasitics and parameters of the other components such as gate resistors and FETs.

    Let me know if you have any further questions.

    Thank you,

    William Moore

  • 0 in reply to William Moore
    Prodigy 30 points

    Hi Willian,

    Thank you for answering my question! I am still not very clear about the spec. 

    If the signal is simultaneously applied at the inputs of two channels, will the chip ensure the rising edge signal won't happen earlier than the falling edge signal at the output?

    Kaiyu 

  • 0 in reply to Kaiyu Wang
    TI__Genius 9865 points

    Hey Kaiyu,

    Sorry for any confusion from my last response.

    Because the LMG1205 does not have interlock, there is no guarantee that the falling edge will be before the rising edge of the other channel with dead times below 8ns. For delay matching, that is the measurement of how different the propagation delay on the high signal vs the low signal can be. So, you would need a bare minimum of 8ns of dead time to ensure that there is no shoot through.

    Let me know if you have any further questions.

    Thank you,

    William Moore