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LM5140-Q1: How to calculate the power loss on gate resistor

Arie Li
Expert 3390 points
Part Number: LM5140-Q1

Hi Experts,

How to calculate the power loss on the gate drive resistor as below? Can I use the formula P=Qg*Vho*fsw*Rg/(Rg+rdson)?(Qg is the gate charge of the external MOSFET, Vho is the gate drive voltage, Rg is the external gate resistor, rdson is the rdson of the internal driver MOSFET). What's the rdson value of the internal driver?

  • 0
    TI__Guru 73842 points

    Hi Arie,

    That equation is correct. You can calculate the resistances from the datasheet EC table (based on the voltage drop for a given current).

    PS: there's generally no need for a gate resistor on the low-side FET The high-side FET controls the switching in a buck regulator.

    Regards,

    Tim