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LM5106: Maximum allowable deatime setting for LM5106

Wei-Hao Chen (TW-FAE)
Expert 3260 points
Part Number: LM5106

Hi Support Team Champs:

My customer has one question regarding what is the maximum allowable dead time setting for LM5106? Datasheet suggested the RDT resistor should be 10k to 150k. But in my customer's design they need at least 1.5us of deadtime, can we increase the resistor to around 300k to get 1.5us deadtime? What is the maximum allowable RT resistor value?

Thank you.

Best Regards,

Wei-Hao

  • 0
    TI__Genius 12990 points
    Hi Wei,

    Good to hear from you, thanks for reaching out!
    Extrapolating the DT curve to 1.5us should not be an issue, but with more impedance on this pin producing a smaller bias current it will make the pin more susceptible to noise fluctuations. Let me procure LM5106 and test this DT out with a 300kohm resistor to make sure we foresee no issue.

    I will update you soon!
    Thanks,
  • 0
    TI__Genius 12990 points
    Hi Wei!

    Sorry for the late reply. I have procured LM5106 and will begin testing. Ill update you asap.

    Thanks,
  • 0 in reply to Jeffrey Mueller
    TI__Genius 12990 points

    Hi Wei,

    After putting the part on the bench, I captured the following waveforms. The DT is set by a ~300kohm and results in ~1.5us. The voltage on the DT pin can be seen as well to be ~3.17 however as discussed before, due to more impedance on this pin there will be a smaller current source and signal to noise ratio on this pin. The max DT voltage is specd at 3.3V so this doesnt leave much headroom for fluctuations, as can be seen during  simply switching the input with no filter, a noisey ground will certainly be of concern.

    purple: Input

    green: HO

    yellow: LO

    purple: Input

    green: V_RDT

    What is the purpose/application of using this DT setting outside the datasheet limit?  

    Please reach out to me so I can give you a more detailed answer to help win this socket.

    Thanks,

  • 0 in reply to Jeffrey Mueller
    TI__Expert 3260 points
    Hi Jeff,

    Thank you so much for setting up the bench test for us. I will follow up the project status with you in a separate email.

    Best Regards,
    Wei-Hao