Analysis of Overload of a Charge-Pump PLL

Eun-Chang CHOI  Bhum-Cheol LEE  Hee-Young JUNG  Kwon-Chul PARK  

IEICE TRANSACTIONS on Communications   Vol.E80-B   No.12   pp.1770-1779
Publication Date: 1997/12/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Communication Device and Circuit
charge-pump,  overload,  stability,  phase-locked loop (PLL),  

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In this paper, we analyze overload and stability in the charge-pump phase locked loop (PLL). We propose a new computational model that can be applied for the precise estimation of the physical limits of charge-pump, the leakage current of loop filter and waveform distortion of charge-pump PLL operating in high speed. We derive the exact mathematical expressions of the parameters describing the steady-state behavior of the PLL as well as the transient-state behavior. Performance comparisons with the conventional model are provided through numerical results. Algorithms for approximate analysis is also provided. The new model is particularity useful for analyzing the cases that the charge-pump PLL operates in high- speed or the loop filter has large leakage current.