TIDA-01505: UCC28C43 PWM controller

Part Number:TIDA-01505

Hi, 

Below are few queries related to PWM controller, could you  please reply on below queries.

1. Does UCC28C43 have variable duty cycle linearly or will only function as switch from 100% on to ~0% duty cycle? Mentioned datasheet value of Vfb for PWM duty cycle   2.6<Vfb<2.4 seems to be operating as switch
2. There are few instances where set frequency of PWM go to half the ser frequency and 50% duty cycle.

Regards

Smitha M S