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DRV8308: Control of this gate driver

Part Number: DRV8308

We are considering using the DRV8308 gate driver to drive a 3 phase BLDC motor as it is sensored and controls the motor sinusoidally. Am I correct in saying the speed can be controlled by either, CLOCK FREQUENCY MODE changing the frequency of a clock signal provided to the CLKIN pin with the frequency of the clock signal equalling the frequency the motor should spin at, CLOCK PWM MODE changing the duty cycle  to scale the speed of the motor from a higher speed (what would this speed be?) down to a lower speed (what would the lower speed limit be?) OR INTERNAL REGISTER PWM MODE which I do not quite understand how this speed control method works?

How do you determine/ how do you instruct the DRV8308 which speed control method you will use? 

Does it matter if the Hall effect sensors are 60° or 120° physically displaced around the motor? Can the DRB8308 be used in either case?


because CLOCK PWM MODE and INTERNAL REGISTER PWM MODE are open loop control methods, does this mean the output/ actual speed of the motor is not monitored and if the seed were to change because of a road change, for example, the DRV8308 would not correct this?

Is there a dev kit available for this motor driver?

  • Hi Michael,

    Your understanding about the CLOCK FREQUENCY MODE and CLOCK PWM MODE is correct. In INTERNAL REGISTER PWM MODE, input PWM duty cycle is calculated by dividing register SPEED by 4095. 

    The mode used is set by the SPDMODE register (address 0x00 bit 5:4). 

    If the hall signals are displaced, timings can be advanced or delayed by tuning ADVANCE register.

    In open loop actual speed is not monitored and the speed might vary when the load changes. 

    Here's the link to DRV8308 EVM:



  • Hi Michael, 

    Can you let us know if the problem has been resolved? 

    Please let us know if further support is needed on this question. Thanks 

    Best Regards,