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DRV8706-Q1: PWM Duty and PWM Frequency

Part Number: DRV8706-Q1
Other Parts Discussed in Thread: DRV8714-Q1

Hello team

This question is for DRV8706-Q1 and DRV8714-Q1.

Duty

We would like to achieve 0 - 100% duty. And PWM step wanted to be less than 1%.

(It means 10% --> 12% --> 14% is not good. 10% --> 10.5% --> 11% is okay)

Our motor driver is analog input so I think there is no actual step but are there any limitation of the resolution??

How to think this?

Max PWM Freq

How to think about the maximum PWM frequency?

Thank you for the support!

Regards,

Hirata

  • Hi Hirata san

    Duty Cycle:

    As you mentioned, this is analog input therefore no step limitation by device. 

    This is just general topic, however any motor driver could not drive very close to 0% or 100%. For example, 0.5%(99.5%) pulse cannot be done due to rise/fall time and propagation delay. Just FYI.

    Max PWM Frequency

    Quick summary is up to 100KHz is reasonable range for both devices. Appreciated if you can share customer's request of max PWM frequency. Is 100KHz enough?

    Please refer DRV8714 Datasheet 9.2.2.1.4. 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.

    These system parameters include:

    • The rise and fall times of the external MOSFETs.

    • The MOSFET QG and load on the charge pump.

    • The minimum and maximum duty cycle requirements (Ex. 10% to 90%)

    DRV8706 is also same(Datasheet 7.1), however it has SPEC to mentions 200KHz as PWM logic input (Datasheet 6.3).

    regards

    Shinya Morita

  • Hello Morita-san,

    Thanks for your detailed explanation. I understand the overview.

    Regarding below, I do not find "200kHz" in the D/S on the web.

    Do I miss something? Which one do you mention?

    I appreciate your support.

    Regards,

    Hirata

  • Hi Hirata san

    Let me correct as follows.

    DRV8706 is also same.

    Sorry for confusion. I was checking different one for DRV8706.

    regards

    Shinya Morita

  • Hello Morita-san,

    I understood.

    Thanks for your answer.

    I will answer to the customer that DRV8706-Q1 can support up to 100kHz.

    I appreciate your support.

    Regards,

    Hirata