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LM5050-1: Adding Schottky in parallel

Jack Sato
Prodigy 70 points
Part Number: LM5050-1

Tool/software:

Hi team,

Is it possible to place Schottky diode in parallel with MOSFET to start quickly?
Most of MOSFET has 0.8V or higher VSD of body diode.

I want to decrease VSD to begin charging MOSFET gate more quickly.

If I added Schottky diode in parallel, what kind of risk would be seen?

Thanks,

  

  • 0
    TI__Mastermind 47230 points

    Hi Jack,

    How will adding Schottky help in faster charging of the GATE?

    Although you can add it for lower power dissipation when the GATE is low.

    Regards,

    Shiven Dhir

  • 0 in reply to Shiven Dhir
    Prodigy 70 points

    Hi Shiven,

    In case of ORing application, if the voltage of PS1 > voltage of PS2, my understanding is that in order for the power supply to change from PS1 to PS2, the voltage on the load side must drop by the VDS of the MOSFET (about 0.8V) after the supply on the PS1 side is stopped in order for the GATE of the FET on the PS2 side I understand that the charge of the GATE of the FET on the PS2 side does not start.

    I thought that by placing the Schottky in parallel, I could reduce the 0.8V to the VF of the Schottky (0.5-0.6V).
    Are there any way to reduce voltage drop during switching power supply?

    Thanks

    Jack Sato

  • 0 in reply to Jack Sato
    TI__Mastermind 47230 points

    Hi Jack,

    The threshold for turning off one of the GATEs due to reverse current blocking is -28mV (typ).

    If PS1>PS2.

    Example PS1 = 14V, PS2 = 12V, PS2 will not go high until PS1 falls to 11.97V. 

    You do not need a drop of 0.8V for PS2 to get active. 

    This is the behavior when 50V supply was turned off and 48V supply takes over. There will no drop of body diode.

    Regards,

    Shiven Dhir

  • 0 in reply to Shiven Dhir
    Prodigy 70 points

    Hi Shiven,

    Thanks for your reply
    We are using external MOSFET, infineon IPB017N10N5LF.

    PS1=52V, PS2=48V
    What we saw is shown below

    Is drop voltage caused by gate charge time delay? 

    Regards

    Jack Sato  

  • +1 in reply to Jack Sato
    TI__Mastermind 47230 points

    Hi Jack,

    Yes, drop voltage is because of gate charge time.

    Regards,

    Shiven Dhir