• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 39 subscribers
  • Views 288 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

PMP31349: PFM ability of LM5148 when used with LMG2100

Jason Jackrel
Prodigy 10 points
Part Number: PMP31349
Other Parts Discussed in Thread: LM5148, , PMP31344

Tool/software:

Hi,

I am working on creating a buck converter with 24-60V input, 12V output, 5A continuous with peak of 20A. My basis is going around the PMP31349 reference design. I was wondering on the design, why the SW node of the LM5148 is connected directly to GND, and is not connected to the SW node coming out of the LMG2100 GAN half-bridge. In the design, it is setup to run in only PFWM, and for efficiency concerns, I would like PFM enabled due to requiring light load efficiency, 

1) is it possible to connect these?
2) can PFM or diode emulation work with the external FET driver and no SW node connected?

  • 0
    TI__Mastermind 41800 points

    Hi Jason, this is currently being looked into and answer will be posted when available. thanks!

  • +1
    TI__Expert 7695 points

    Hi Jason,

    Thanks for contacting us.

    In this design, we have connected the SW node of LM5148 to GND to provide a logic level (GND referenced) gate driver signal to the HI pin of the LMG2100 half bridge.

     If you connect it to the actual SW node, your HO/HI signals will be referenced to the SW node. This would be ok if you use separate switches, but not if you use the LMG2100 half bridge: please refer to the Recommended Operating Conditions table in the device datasheet LMG2100R044 100V, 35A GaN Half-Bridge Power Stage datasheet (Rev. B).

    I have checked internally, and we believe that the PFM mode should still be available when connecting SW node to GND. However, we have NOT tested the PMP31344 board in this configuration yet. The design should also be properly verified and optimized when operating in PFM mode.

    Thanks,

    Stefano

  • 0 in reply to Stefano Panaro
    Prodigy 10 points

    Thank you! Grounding switching node to makes much more sense under that context. Will try it on my board. 

  • 0
    TI__Expert 7695 points

    Jason,

    There has been a further investigation from the team, and we are not confident that we can guarantee a proper operation in the proposed configuration (PFM mode with GaN and LM5148 with SW node shorted to GND).

    The proposed configuration is therefore NOT recommended.

    It would be better to select FPWM mode when using the PMP31349 schematic.

    Thanks,

    Stefano