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LM5116: high value gate resistor

Aivaras Sakauskas
Intellectual 1600 points
Part Number: LM5116

Hi,

We have done some EMC testing and have experienced some issues with radiated emissions around 30 MHz. A 22 ohm has been used as the gate resistor in our design which has reduced the emissions to acceptable limits. The datasheet recommends values not higher than 10ohm. 
Could you provide some insight into what potential issues may arise from a gate resistor like this?
Thanks
  • 0
    TI__Mastermind 23845 points

    Hi Aivaras,

    I believe this is related to the power dissipation of the FETs, The larger the resistor value, the slower the FETs is going to be turned on. 

    Hence more switching loss. But on the other hand, the EMC will get better since now you don't have a high dv/dt transition on the switch node. 

    Another option is to put a snubber circuit on the switch node to have a lower dv/dt in the SW pin

    Thanks

    -Arief