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tps43061 using same highside and lowside fet

Yubo Qiu34
Prodigy 20 points
Other Parts Discussed in Thread: CSD, CSD16340Q3, CSD16323Q3

I am building a boost converter, and I'm using Webench, but it uses different FETs for high side and low side. Why doesn't it use the same FET for both? Is it ok if I use the same FETs? my parameters are this:

Vin = 5.5V- 8.6V

output=14V@4.3A

  • 0
    TI__Mastermind 35115 points

    Hi Yubo,

    You can use the same FET for each. Typically different FETs are used to optimize the design because there are different specifications that are more important for each MOSFET to minimize power loss increasing efficiency.

    Best Regards,
    Anthony

  • 0 in reply to Anthony F
    Prodigy 20 points

    So i guess a follow up question would be this: what would be the reasoning for using the CSD17304 for the high side FET and CSD 16323 for the low side FET as suggested by Webench? i.e. what optimizations or inefficiencies should I be aware of?

  • 0 in reply to Yubo Qiu34
    TI__Mastermind 35115 points

    Generally the low-side MOSFET selected has lower gate charge so it can turn on and off faster to reduce switching loss. The high-side MOSFET has lower Rdson to reduce its conduction loss and its switching speed is less important to reduce loss. The CSD16340Q3 and CSD16323Q3 are very similar so the change in performance will be small if you were to use two of the same. The CSD16323Q3 does have slightly lower gate charge and this is why it was selected for the low-side MOSFET.