Analysis of a charge-pump PLL: a new model

A new model for the analysis of a second-order charge-pump phase-locked loop (PLL) is described. This model uses a set of difference equations in two well-chosen state variables. It allows one to model exactly the transient behavior of the PLL, even if the loop is out of lock. Theoretical stability and overload limits are determined. A continuous-time approximation is derived. Its validity is verified by simulation examples.< >