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DRV8714-Q1: Dead time/ blanking time minimum

Geraldine Baret
Intellectual 2585 points
Part Number: DRV8714-Q1

Hello,

I am trying to check if I could set the switching frequency to 400kHz but I saw on the datasheet that the dead time/blanking time is at 8us. At 400 kHz the PWM period is 2,5 us, so I would need the blanking time to be much less than that.

 

The charge pump frequency is mentioned to be at 400kHz on the datasheet, my understanding is that we can set the frequency to 400 kHz.

           1)Could you please tell me, what is the minimum blanking time that can be set for the DRV8714?

           2)Would that mean that we cannot have the switching frequency at 400kHz?

Thank you in advance,

Geraldine

  • 0
    TI__Guru 55605 points

    Geraldine,

    The blanking time specification is not the real limitation for the device.  The frequency limitation is discussed in detail in section 9.2.2 in the datasheet.

    What is the reason to request such a high switching frequency?  What is the application?  

    Regards,

    Ryan

  • 0
    Genius 5040 points
    Geraldine Baret said:
    I am trying to check if I could set the switching frequency to 400kHz but I saw on the datasheet that the dead time/blanking time is at 8us. At 400 kHz the PWM period is 2,5 us, so I would need the blanking time to be much less than that.

    The datasheet says the max PWM input is 100Khz (or lower depends on other factors), so you cannot use 400Khz pwm.

    "9.2.2.1.4 Maximum PWM Switching Frequency The maximum PWM frequency of the driver is typically determined by multiple factors in the system. While the DRV871x-Q1 device can support up to 100kHz, system parameters may limit this to a lower value."

    BTW, the typical deadtime is 350ns, with additional deadtime can be added using the SPI serial data interface.

    Brian

  • 0
    TI__Intellectual 2585 points
    Ryan Kehr said:
    What is the reason to request such a high switching frequency?  What is the application?  

    We are trying to use the DRV8xxx as a power supply. We want to use it in an automotive application.

    Thank you for your input and support.

    Geraldine 

  • 0 in reply to Brian Dang
    TI__Intellectual 2585 points
    Brian Dang said:
    "9.2.2.1.4 Maximum PWM Switching Frequency The maximum PWM frequency of the driver is typically determined by multiple factors in the system. While the DRV871x-Q1 device can support up to 100kHz, system parameters may limit this to a lower value."

    What is the factors that limit the maximum PWM frequency? Could there be a way to have a higher fsw or is there a DRV8xxx that can support this frequency?

    Thanks,

    Geraldine

  • 0 in reply to Geraldine Baret
    TI__Guru 55605 points

    Geraldine,

    Please read section 9.2.2 in the datasheet completely.  There are multiple limitations discussed in this section.

    Please consider one of TI's many automotive qualified power controllers as an alternative.

    Something like this might work for you:

    https://www.ti.com/lit/ds/symlink/tps40090-q1.pdf

    Regards,

    Ryan