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DRV8711: used with CSD88537ND mosfet gives EMI issues

Guido Vermeulen
Prodigy 65 points
Part Number: DRV8711
Other Parts Discussed in Thread: CSD88537ND

We developed motor driver with the DRV8711 driver and CSD88537ND mosfet almost similar to the design in the following blog:

e2e.ti.com/.../spin-it-designing-your-own-motor-drive-and-control-system-part-4

We have added gate resistors because we use a 2.8A motor. During EMI testing we discovered the following:

120R Gate resistors at low side only will not pass the EMI test.

120R Gate resistors at low and high side will not pass the EMI test

240R Gate resistors at low and high side will just pass the EMI test

We used the following settings: IdriveP = 50mA, IdriveN = 100mA and Tdrive = 250ns (larger drive currents gave worse results)

My questions:

1)

In the datasheet there is mentioned only place 47R to 120R gate resistors at the low side. With these resistor values we will not pass the EMI test.

Can we use the 240R resistors (or even higher) so we can pass the EMI test?

2)

Are there settings (besides Idrive and Tdrive) which we can check to improve EMI?

3)

Are there any other options to improve EMI (based on the design from the blog)?

  • 0
    TI__Guru** 114905 points

    Hi Guido,

    Increasing the gate resistors may help, but there are risks associated with doing so. There is a possibility of shoot-through if the FETs is not disabled when the other FET is being enabled.

    Assuming you already have the dead time set to 850ns, there are no more register settings to adjust.

    Can you provide more information, such as:

    Plots of the EMI failures
    The schematic and layout. This can be a snippet of the DRV8711.
    If you desire, we can make arrangement to communicate this privately.

  • 0 in reply to Rick Duncan
    Prodigy 65 points

    Hello Rick,

    Thanks for your response. The dead time is indeed 850ns.

    I would like to share the details with you. Please let me know how I can do this privately.

    Kind regards,

    Guido

  • 0 in reply to Guido Vermeulen
    TI__Guru** 114905 points

    Hi Guido,

    Thanks for sharing the information. At this time we will close this thread and communicate privately.

    If there are some generic findings that help others, we may include our findings at a later date.