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DRV8306: Effect by regenerative electric power

Hirotaka Matsumoto
Guru 27585 points
Part Number: DRV8306

Hi all

Would you mind if we ask DRV8306?
Please refer to the attachment file.
20190215_DRV8306.pdf
Could you give us advice?

Kind regards,

Hirotaka Matsumoto

  • 0
    TI__Guru 65390 points
    Matsumoto-San,

    When the motor is stopped, what is the method? Is the PWM reduced directly from 90% to 0%? Is there any braking used? Do they have access to the nBRAKE pin?

    Regards,

    -Adam
  • 0 in reply to Adam Sidelsky
    Guru 27585 points

    Adam san

    Thank you so much for your reply.

    When the motor is stopped, what is the method? Is the PWM reduced directly from 90% to 0%?
    ->Yes, they operate the PWM reduced directly from 90% to 0%.

    Is there any braking used? Do they have access to the nBRAKE pin?
    ->We will confirm it. Using nBrake pin(pull-low?).
       The nBRAKE input halts the motor by turning off all high-side MOSFETs and turning on all low-side MOSFETs when it is pulled low.
       With turning on all low-side MOSFETs, according to slow decay, does it mean to prevent current flow from L to VM via FET's body diode?

    And then, is it possbile to  separate DRV8306's VM(+VDRAIN) and FET's VM(FET's drain voltage)?
    With separating voltage, it is not recommend.
    We assume that this affects for OCP protection operation and normal operation.
    (It is necessary that DRV8306's VM(+VDRAIN) is more than FET's VM(FET's drain voltage).)
    If you have some advice, could you let us know?

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Guru 65390 points
    Matsumoto-San,

    When the motor is spinning at 90%, there is a lot of energy in the system. When the duty cycle is reduced from 90% to 0% very quickly without braking, there is no place for that energy to go, this can cause many problems.

    The better way to reduce speed of the output is to use the nBrake pin or to bring down the PWM rate "slowly". Even if this slowing occurs over some mS, this will help significantly.

    Using the Brake will allow the low-side FETs to recirculate the current while the motor slows down. This should prevent supply pumping.

    We do not advise separating the VM and VDRAIN.

    Regards,

    -Adam
  • 0 in reply to Adam Sidelsky
    Guru 27585 points

    Adam san

    Thank you so much for your reply.
    OK, we got it.

    Kind regards,

    Hirotaka Matsumoto