Optimum phase-acquisition technique for charge-pump PLL

Abstract

In this paper, we propose a new optimum phase-acquisition algorithm controlling the loop gain of a charge-pump PLL (CP-PLL) in the sense of the MMSE criterion. A set of recursive difference equations minimizing RMS jitter of output phase is derived to obtain an optimum gear-shifting sequence with a zero-phase start (ZPS) assumption. It is shown that the optimum gear-shifting sequence is independent of the variance of the input phase jitter. A procedure for applying this sequence to the design of CP-PLL circuits is described, Both behavoral simulation and HSPICE circuit-level simulation demonstrate that the proposed design leads to an efficient CP-PLL having both fast acquisition and significant jitter reduction characteristics. The optimal gear-shifting CP-PLL outperforms the conventional CP-PLLs. These methods can be used for clock recovery applications such as data communication receivers, disk drive read/write channels, and local area networks, as well as for other applications requiring very short initial preamble periods.