A dividing ratio changeable digital PLL based on phase state memory and double clock‐edge detection

Abstract

SUMMARYIn this paper, we propose a dividing ratio changeable digital phase-locked loop (PLL) based on phase state memory and double clock-edge detection that satisfies the three characteristics of low jitter, wide lock-in range, and fast pull-in at the same time. The counter for the double edge detection of the base clock reduces the circuit scale by using a selector. In the steady state, the output jitter of the proposed digital PLL is always a half pulse width of the base clock regardless of the frequency fluctuation of the base clock. Also, the upper bound frequency of the lock-in range becomes six times that of the conventional dividing ratio changeable PLL, when the permissible output jitter is identical. Furthermore, the fast pull-in is finished in one cycle of the input signal and the pulse width of the multiplication output signal becomes almost constant.

Multiple‐frequency digital phase‐locked loop based on multiphase clock divider with constant pulse interval

“…To improve this situation, dividing ratio changeable DPLL (DCPLL) was proposed; in such circuit, conventionally fixed ratio of divider in the loop is varied with frequency of input signal. DCPLL features very wide lock‐in range as compared to conventional DPLL, thus promising versatility.…”