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Significance of Resistor (R523_B) used between Gate and Source of N channel MOSFET in Buck converter?

Rackshith pg
Prodigy 100 points

Why this 100K Resistor Used between Gate and Source?

Why 100K? Any tolerance recommended for this Resistor?

What is the significance of this Resistor (R523_B) used between Gate and Source of N channel MOSFET. in synchronous Buck converter application.

Do we have any application note on this?

  • 0
    TI__Mastermind 18266 points

    The resistor is there to pull down Vgs to 0V when the driver is unpowered or its output is otherwise High-Z.

    The designer of this circuit must have determined that 100k would burn a sufficiently small thermal power in normal operation to prevent a long term reliability concern, and at the same time was low enough to drain any charge injection into this capacitance with a sufficently low noise floor to avoid leaving the switch ON during start-up.

    I don't think that tight tolerance is required here at all. Simply make sure the power rating is at least double what the expected power is in normal operation. Triple to be safe.

    Our comprehensive primer does mention this component, if you would like to review section 6:

    https://www.ti.com/lit/ml/slua618a/slua618a.pdf 

    It is not exatly the same, but it is an application where this component is much more critical and is discussed in more detail than I have.

    Best regards,

    Sean