International audienceThe charge pump phase locked loop (CP-PLL) is widely used subsystem in modern mixed-signal electronic systems that are utilized in digital and wireless applications such as clock generation, synchronization and frequency synthesis. In the classical mode, the combination of a current switched charge pump and a digital phase and frequency detector (CP-PFD) circuits produces an ideal pulse width modulated constant current during one sampling period, which permits a suitable transient performance. Nevertheless, many commercially used CP-PLL chips (e.g., 4046 family) have a voltage switched charge pump (VSCP) because the design of the constant voltage source is easier than the constant current generator and it is a low cost solution. However, the VSCP delivers a non-constant pump current, which varies during one sampling period related to the electrical load of the loop filter (LF). This effect results in a varying gain of the control system affecting significantly its tracking ability. Furthermore, due to its hybrid structure, the simulation of the CP-PLL at high frequencies is challenging and the analysis of its transient characteristics during its non-linear acquisition procedure is not easy. In this paper, a first ever exact and nonlinear model based on the phase equations of the second order voltage switched charge pump phase locked loop (VSCP-PLL) is established by using an event driven (ED) technique. This exact model is then simplified by using a step-wise quasi-constant current approximation during one sampling period to obtain the analytical phase equations. The derived ED-model is validated at transistor level simulations using 130 nm CMOS process. Furthermore, some typical nonlinear features of the VSCP-PLL are explored and the developed ED-models are compared with the quasi-time-continuous (QTC) theory

The simulation of charge-pump phase-locked loops (CP-PLL) is a challenge within the design. The problem is related to the mixed-signal and nonlinear behavior as well as the existence of high and low frequency functional blocks. Here a methodology is presented for the efficient and accurate simulation and analysis of the transient characteristic. For this, nonidealities like dead-zone, current/timing mismatches, leakage current and the nonlinear voltage controlled oscillator characteristic are considered. Moreover, the proposed technique is applied to CP-PLL systems with arbitrary loop filters by using the solution of the analog parts of the differential equation system and by solving the phase equation of the system with regard to the switching instant of time of the phase and frequency detector

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The GARDNER's stability theory is vital for linear modeling and empirical design of the 2nd and 3rd order charge-pump phase locked loop (CP-PLL). This criterion is general to identify the stability boundary in the steady state. It has been particularly applied to the PLL with a conventional current switched charge-pump (CSCP). Ideally, the CSCP supplies symmetrical pump currents. In some applications a voltage switched charge-pump (VSCP) is implied, which offers design simplicity and low cost. The VSCP architecture delivers an unequal amount of pump currents to the loop filter (LF), which introduces an additional and curious non-linearity in the behavior. This peculiarity buried in the second order voltage switched CP-PLL may disqualify it in several serious applications, where a symmetrical pump current is suitable. In this paper GARDNER's stability boundary is investigated by making iterative transient simulations using the event-driven model of the second order voltage switched CP-PLL. The simulated results near fixed point from the second order voltage switched CP-PLL show that, the stability boundary is non-conservative in such system, eradicating the overloading from the current switched charge-pump