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LM5050 with parallel mosfets

Derek King1
Intellectual 365 points
Other Parts Discussed in Thread: LM5050-1

I have an application where the current levels may require two MOSFETs to placed in parallel with an LM5050-1

Are there any recommendations about for paralleling MOSFET with the LM5050?  

For best heat dissipation, the FETs will be place farther apart.   However, I'm worried about the gate signal ringing with high-speed turn-off events.   In my previous designs the LM5050-1 was placed closely to the FET and used short (<1cm) trace lengths.   With two FETs, the traces will be much longer.  

Questions:

1. If the FETs are placed farther apart (say >3cm), would it be a good idea to put resistor on each mosfet gate signals to prevent gate from ringing during fast turn-off events?

2.  If gate resistor is used, the LM5050's internal gate clamping zener will be less effective.   Should an external zener be used in this case?

  • 0
    TI__Mastermind 41790 points

    Hi Derek,

    I think you got it right on. Gate resistors should be used if you expect some parasitic inductance in your design and soften the turn off of the FETs. Having two FETs in parallel will increase total gate capacitance so I wouldn't be opposed to having an external zener from gate to source.

    Regards,

    Darwin