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Hier finden Sie wissenschaftliche Publikationen aus den FraunhoferInstituten. Event driven modeling and characterization of the second order voltage switched charge pump PLL
 IEEE transactions on circuits and systems. 1, Fundamental theory and applications 63 (2016), No.3, pp.347358 ISSN: 10577122 ISSN: 15498328 

 English 
 Journal Article 
 Fraunhofer ENAS () 
Abstract
The charge pump phase locked loop (CPPLL) is widely used subsystem in modern mixedsignal 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 (CPPFD) circuits produces an ideal pulse width modulated constant current during one sampling period, which permits a suitable transient performance. Nevertheless, many commercially used CPPLL 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 nonconstant 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 CPPLL at high frequencies is challenging and the analysis of its transient characteristics during its nonlinear 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 (VSCPPLL) is established by using an event driven (ED) technique. This exact model is then simplified by using a stepwise quasiconstant current approximation during one sampling period to obtain the analytical phase equations. The derived EDmodel is validated at transistor level simulations using 130 nm CMOS process. Furthermore, some typical nonlinear features of the VSCPPLL are explored and the developed EDmodels are compared with the quasitimecontinuous (QTC) theory.