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Clock and Data Distribution Products Pt1 Slide 6

In order to better understand the concepts that have been discussed, this slide provides a practical example. The objective is to determine the output frequency based on the input frequency and the listed values for the pre-divider (P), the output divider (N) and the feedback divider (M). First, there are some necessary equations. It was previously mentioned that the frequencies of the two input signals to the PFD have to be equal. The VCO will speed up or slow down until the inputs to the PFD are in phase and equal in frequency. Therefore it can be concluded that feedback frequency, Ffb, is equal to input frequency Fin divided by P. From the same logical deduction, it is possible to conclude that the output frequency of the VCO, Fvco, must be equal to the input frequency, Fin, divided by the pre-divider, P, and multiplied by the feedback divider, M. Having calculated the frequency of the VCO, the output frequency can be calculated by dividing it by the output divider, N. Please take some time to calculate the VCO frequency and the output frequency, the solution will be shown on the following slide.

PTM Published on: 2014-08-04