Do different divide ratios cause variations in jitter?
Ideally, no. Jitter remains the same as a signal is divided by different ratios. However, phase noise is frequency dependent. With the AD951x parts, there is a slight jitter difference between the divide-by-1 case (divider bypassed) and the 2-32 ratios. When a 2-32 divide-by is chosen there is a slight jitter contribution by the divider, but this is ratio independent. This is because the signal path is different than in the divide-by-1 case which does not incur the additional jitter contribution of the divider.