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UCC21540: can 2 driver in one UCC21540 be used to drive 2 parallel mosfet

Hale Tan
Expert 3170 points
Part Number: UCC21540

Hi team,

I see that the UCC21540 can be used for two low side drivers, two high-side drivers, or a half-bridge driver? So can 2 driver in one UCC21540 be used to drive 2 parallel mosfet if 1 gate driver is not enough? Or more parallel UCC21540 to drive more mosfet? The max delay match time is 5ns. If ther are existing 5 ns delay time between 2 driver, can they be used to drive 2 parallel mosfet?

  • 0
    TI__Genius 17646 points

    Hi Hale, 

    The problem with using two gate drivers to drive one switch is that the driver outputs will be shorted together. Any mismatch in propagation delay will short circuit both of the outputs. Usually you need to add a "make before break" gate resistance in order to tie two output stages together, which defeats the purpose. I believe that a better solution is to use a larger single driver, or use an external current buffer if you indeed need more output current. If you have two drivers and two mosfets, you can absolutely use one driver to drive one mosfet, and another driver to drive a parallel mosfet. If there is a short propagation mismatch, one switch can easily handle all of the current for a short duration.

    There problem with using one gate driver to drive multiple mosfets is that the drive strength will be weaker. This is a good thing for turning high-side switches "ON", but to strengthen the "OFF" drive, you can use a local PNP turn-off circuit for each individual mosfet.

    You should consider using larger mosfets and maybe even a module instead of parallel switches. Layout will become a limiting factor in a paralleled design, and I think you can sometimes get to a better performing inverter faster if you can "outsource" the high current density layout by using a module.

    Best regards,

    Sean