the basic structure and operating principle of ADPLL(All Digital Phase-Locked Loop) are first introduced
which is followed by the analyses of its mathematic model and the calculation of its main parameters.Then
a feasible low-jitter ADPLL circuit structure for SEC(SDH equipment clock)is designed and specific circuit analysis of and designs for each part of ADPLL made
which is optimized by appropriate CPU configurations.Finally
this circuit is verified by FPGA and the test result given.