8.3.9 Fractional Engine

The delta signal modulator is a key component of the fractional engine and is involved in noise shaping for better phase noise and spurs in the band of interest. The order of the delta sigma modulator is selectable between the integer mode and third order for fractional PLL mode, and it can be programmed in R33[1:0]. Dithering can be programmed in R33[3:2] and should be disabled for integer PLL mode and set to weak for fractional PLL mode.