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How to choose proper MOSFET for Drone ESC

Young Hu
Expert 4185 points
Other Parts Discussed in Thread: DRV8305, TMS320F28027F, CSD18509Q5B

Hi Champs,

I am designing an ESC for my customer. TMS320F28027F+DRV8305+NexFET are being promoted to customer, and the control method is sensorless FOC. The system specs are as follows:

1. 22.2V DC bus voltage (6S lithium battery);

2. DC bus current would be high to 30A with maximum speed;

From my understanding, 40V or 60V MOSFET would be good enough. Would you suggest how to choose the Id? And also would you help to explain the terms "Continuous Drain Current (Package limited)" and "Continuous Drain Current (Silicon limited)"

Thanks a lot.

BR,

Young

  • 0
    TI__Expert 6755 points
    Young,

    On the TI website there are a series of blogs called understanding the FET datasheet, part 3 of the 6 part series talks about continuous current ratings and is here: e2e.ti.com/.../understanding-mosfet-data-sheets-part-3

    As for selecting a power FET, it is best to select based on power loss bit the current rating, as this is a motor application switching losses will be fairly low due to low frequency and as such as a first approximation I would suggest looking at the FET resistance then doing a quick calculation to determine the power loss with P=I*I*R.
    Then you will need to decide which package you want and f you get the resistance you need in that package or need to parallel FETs to hit the current.

    For instance the CSD18509Q5B is ~1mOhm FET, so losses would be ~30*30*0.001= ~1W, should be not problem for a SON5x6 package to handle in a typical circuit.

    Chris....
  • 0 in reply to Chris Bull
    TI__Expert 4185 points
    Hi Chris,
    You are right. CSD18509Q5B is suitable for this application.
    Many thanks.
    Regards,
    Young