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  • TI Thinks Resolved

TIDA-00915: TIDA-00915 LMG3410

Intellectual 980 points

Replies: 3

Views: 117

Part Number: TIDA-00915

Hello

We are trying to use LMG3140 in designing an inverter.....we understand now that this power switch does not require FWD …...our question is during the 3rd quadrant operation or when the inverter is in braking mode....do we need to give that LMG3410 any control signal or should we leave it switched off?

If we give it a control signal....does this mean that LMG3140 is a bi-directional switch?

Regards

Sam

  • Hi Sam,

    LMG3410 is not a bi-directional switch. Similar to a diode, it can conduct from source to drain. However, the voltage drop for reverse current would be a little higher than a diode. As long as you keep the dead time or 3rd quadrant conduction time short, it should be okay. Also to reduce loss, you can also turn it on for synchronous rectification.

    Thanks and regards,

    Lixing 

  • In reply to Lixing Fu:

    Hi Lixing,
    Thank you for your answer

    we must be missing something....

    * The normal conduction of the LMG is from Drain to Source.....Correct?
    * When the LMG conduct from Drain to Source ….this is effectively 1st Quadrant operation (volt and current across LMG are in direction 1)...….correct?
    * This happens by turning the LMG on......correct?*
    * LMG can also conduct from Source to Drain and hence it is replacing the FWD …..correct?
    * When the LMG conduct from Source to Drain ….this is effectively 3rd Quadrant operation (volt and current across LMG are in direction opposite to direction 1)...….correct?
    * You can also turn the LMG on when conduction is from Source to Drain (3rd quadrant operation)… for synchronous rectification .....correct?

    If all the above is correct I would say LMG is a bi-directional switch.

    If not bi-directional what is missing?

    Regards
    Sam
  • In reply to Sam Ref:

    Hi Sam,

    Thanks for the followup.

    In my understanding a bi-directional switch means that the switch can block voltage from either direction, drain to source, and source to drain. Similarly to regular Si MOSFET, GaN devices cannot block voltage from source to drain. Therefore, neither Si MOSFET or GaN can be called bi-directional switch. GaN devices have very similar feature as Si MOSFET in terms of functionality and conduction, but just different in 3rd quadrant voltage drop.

    Hope this solves your puzzle.

    Thanks and regards,
    Lixing

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