DRV11873: DRV11873 use in pwm

Part Number:DRV11873

HI sir:

     The chip DRV11873 ,I want to use in 4HZ to 20Hz. it means rmp (240-1200). By the datasheet. I think it is suitable. But when i use in slow speed. it don't run smoothly.

Do some notice i need to Focus? Or have other type can be recommend?