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DRV8301 + IRFS3004-7PPbF

Asif Ahmed
Expert 1570 points
Other Parts Discussed in Thread: DRV8301, DRV8305

Hello -

I have been doing a lot of learning up on MOSFET characteristics, gate drivers, etc etc. and have pretty much narrowed down to a couple of MOSFETs for my application. The one I am leaning towards is the IRFS3004-7PPbF (http://www.mouser.com/ds/2/200/irfs3004-7ppbf-84182.pdf.

Here are my application specs:

Instaspin-FOC (so 6 MOSFETS switching simultaneously)

20Khz switching frequency

12-35V input range

~100A continuous current (please assume a sound thermal design for the sake of this analysis)

Based on all of the analysis I have done in trying to fit the IRFS3004-7PPbF to the DRV8301, it seems like this should work quite well. But I would love to hear from the pros if there are some aspects I am still missing.

Thanks very much!

-asifjahmed

  • 0
    TI__Guru** 114905 points

    Hi Asifahmed,

    If you use the worst case Qg of the FETs, you are approaching the limit of 30mA (28.8mA). Since this is a rough approximation, it could be higher.

    I will ping others for their comments.

  • 0
    TI__Mastermind 21320 points

    Hi Asif,

    As Rick mentioned you are approaching the limits of the DRV8301, but anything below 30 mA should be no issue.

    From the gate drive standpoint I don't see any issue. Thermal management will be the tricky part to achieve 100 A.

    One concern is that you are operating close to the VDSS spec of the MOSFET at 35 V. Voltage transients from switching or back-emf of the motor could potentially causes a violation of this spec. It may be recommended to look at a 50-60V MOSFET if you truly want to operate at 35 V, but this will really depend on how well voltage transients are controlled.

  • 0 in reply to Nicholas Oborny
    Expert 1570 points
    Thanks Nick! The highest voltage will actually be an 8S lithium battery, so 33.6 V fully charged. Is there a "rule of thumb" on margin for voltage transients?
  • 0 in reply to Asif Ahmed
    Expert 1570 points
    Also, one more question - it is desirable to use the DRV8305 vs the DRV8301 due to the third integrated shunt amplifier. However, since the DRV8301 has the higher peak current capability, I am assuming that this is better for the relatively large IRFS3004-7PPbFs. Is this a correct assumption?
  • 0 in reply to Asif Ahmed
    TI__Mastermind 21320 points

    Rule of thumb is quite fuzzy ranging anywhere from 1.5x to 2x voltage margin in high power applications. This really all depends on how tightly controlled the transients are though.

    Correct, DRV8305 is a more advanced gate driver but DRV8301/2/3 are more powerful gate drivers (peak current). Their RMS current output (30 mA) is equivalent though.

    The DRV8301/2/3 may make the most sense for voltage margin and higher peak current capability. But the features of the DRV8305 may make it worth designing around.

  • 0 in reply to Nicholas Oborny
    Expert 1570 points

    When you say it may be worth "designing around" the DRV8305, are you implying using MOSFETs that are less demanding? I definitely need to at least attempt to design for 100A peak.

    As for handling voltage transients, is this generally a matter of having enough capacitance in the circuit, or is there some other aspect of the circuitry that i should focus on with regard to "minimizing voltage transients"?

    I understand that you always bring me to the realization that its always a trade-off, depends on many other variables, etc.. - and I appreciate that? I am learning!

  • 0 in reply to Asif Ahmed
    TI__Mastermind 21320 points

    You could design with the existing MOSFETs.

    Examples of common methods to handle voltage transients are bulk capacitance to manage excess energy from motor, TVS clamping circuits, RC snubbers, smaller bypass capacitors to manage higher frequency transients. 

    I actually have a blog that goes over some of these topics.

    e2e.ti.com/.../motor-drive-forum-top-faqs-electrical-overstress

    e2e.ti.com/.../motor-drive-forum-top-faqs-3-methods-to-prevent-electrical-overstress