+ Post New Thread
Results 1 to 5 of 5
  1. #1
    Advanced Member level 2
    Points: 1,914, Level: 10

    Join Date
    Aug 2016
    Posts
    509
    Helped
    4 / 4
    Points
    1,914
    Level
    10

    can boost converters cause gate loop ringing

    MOSFETs can be very inefficient with insufficient Vgs even if peak current is coming from a capable gate driver but at insufficient voltage.

    Would a high frequency switcher such as this MT3608 cause gate loop ringing or other issues for supplying a gate driver which would output ~5amps peak and ~40mA RMS?
    MT3608.pdf

    An electrolytic or larger MLCC can be added to the gate driver supply rail across the recommended 22uF MLCC filter to handle peak currents.
    Last edited by Zak28; 17th June 2019 at 07:52.

    •   AltAdvertisement

        
       

  2. #2
    Super Moderator
    Points: 76,257, Level: 67
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    15,463
    Helped
    3515 / 3515
    Points
    76,257
    Level
    67

    Re: can boost converters cause gate loop ringing

    Hi,

    A gate driver delivering too low voltage is simply "unsuitable" independent of it's current capabilities.
    Choose another, suitable driver.

    As the MT3608 is non isolating, you can just use it for a low side MOSFET.
    The use of it makes no sense in my eyes.
    It's input is DC, it's output us DC and both are connected via GND...thus (the DCDC part) it should not be included in the gate loop.
    (Only the output capacitor)

    RMS is not useful here, better use "average" ... and average current should be rather low. It should be equal to
    Q_gate_tot x frequency.

    I assume any electrolytics - with it's high ESR - is not suitable to support the 22uF MLCC.
    Any additional MLCC will not bring much benefit ... because of the low Q that is drawn by every switch ON.

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



    •   AltAdvertisement

        
       

  3. #3
    Super Moderator
    Points: 258,502, Level: 100
    Awards:
    1st Helpful Member

    Join Date
    Jan 2008
    Location
    Bochum, Germany
    Posts
    45,129
    Helped
    13719 / 13719
    Points
    258,502
    Level
    100

    Re: can boost converters cause gate loop ringing

    To discuss "gate loop" ringing, we should look at the gate driver circuit, not a boost converter data sheet.



    •   AltAdvertisement

        
       

  4. #4
    Advanced Member level 2
    Points: 1,914, Level: 10

    Join Date
    Aug 2016
    Posts
    509
    Helped
    4 / 4
    Points
    1,914
    Level
    10

    Re: can boost converters cause gate loop ringing

    Quote Originally Posted by KlausST View Post
    Hi,

    A gate driver delivering too low voltage is simply "unsuitable" independent of it's current capabilities.
    Choose another, suitable driver.

    As the MT3608 is non isolating, you can just use it for a low side MOSFET.
    The use of it makes no sense in my eyes.
    It's input is DC, it's output us DC and both are connected via GND...thus (the DCDC part) it should not be included in the gate loop.
    (Only the output capacitor)

    RMS is not useful here, better use "average" ... and average current should be rather low. It should be equal to
    Q_gate_tot x frequency.

    I assume any electrolytics - with it's high ESR - is not suitable to support the 22uF MLCC.
    Any additional MLCC will not bring much benefit ... because of the low Q that is drawn by every switch ON.

    Klaus
    I meant the mt3608 for lowside switching and didn't include that in the original description.

    It should serve fine for supplying low side NMOS gate driver?



  5. #5
    Member level 3
    Points: 2,053, Level: 10
    Achievements:
    7 years registered

    Join Date
    Dec 2009
    Location
    USA
    Posts
    54
    Helped
    15 / 15
    Points
    2,053
    Level
    10

    Re: can boost converters cause gate loop ringing

    Quote Originally Posted by Zak28 View Post
    I meant the mt3608 for lowside switching and didn't include that in the original description.

    It should serve fine for supplying low side NMOS gate driver?
    PIN #1 (SW) of the MT3608 is a Low Active MOSFET only, it does not source any current - it is not a Gate Driver - it is the "PWM switch".
    I assume you are trying to add an external MOSFET?
    Please, post a schematic.

    And then clearly explain ...
    How you are going to use the MT3608 to Source current into & Sink current from the Gate of the external MOSFET, without adding a GATE DRIVER?



--[[ ]]--