• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 64 subscribers
  • Views 2594 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM5113 falling edge spikes

Longxiang Wang
Prodigy 30 points
Other Parts Discussed in Thread: LM5113

Hi,

I am really a green hand with GaN. 

I am using the spice model of LM5113 provided by TI on LT spice. It is intended for Pspice, but it is working on LTspice anyway.

My question is why I see strange spikes on the falling edge on both high side and low side output voltage? It is understandable if these spikes happens during the rising edge due to parasitic inductance resonance with Ciss.

  • 0
    TI__Expert 4710 points

    Hi Longxiang,

    the waveform you are showing is not something that is typically expected. 

    Here are a few thoughts that might help clean it up:

    1.  It does not appear that you have left enough dead time between the high and low side. Shoot-though conditions might cause a spike: changes on either Cgd or Cgs can interfere with the Vgs when the driver is still transitioning.Increase the dead time so that you can clearly see one signal reaching zero, before the other signal turning on.
    2. To discount all the parasitic ringing (which I don’t think it to be the cause) slow down the edge rates for the FETs and observe changes. Remember to allow for extra dead time.
    3. It could be the cause of some parameter in the FET model interacting with the LM5113 model. Try this circuit with a different set of FETs.

     

    Hope this helps.

    Regards,

    Alberto

  • 0 in reply to Alberto Doronzo
    Prodigy 30 points

    Hi Alberto,

    Thanks for your reply.

    Even if I give enough dead time to eliminate any possible shoot-through, spikes are still there, so this does not seem to be the root cause.

    Also, trying out other GaN FETs or normal MOSFETs does not help.

    Could it be that the transient model from TI is designed for Pspice and using it in LT spice might cause strange behavior?

    regards, Longxiang

  • 0 in reply to Longxiang Wang
    TI__Expert 4710 points
    Hi Longxiang,

    it could be caused by the way the model is read and reacts to transients in LT spice.
    Unfortunately I would not be able to replicate this on the same simulator.

    Feel free to contact us in case you need further assistance.

    Regards,
    Alberto