A sub-mA phase-locked loop fabricated in a 65nm standard digital CMOS process is presented. The impact of process variation is largely removed by a novel open-loop calibration that is performed only during start-up but is opened during normal operation. This method reduces calibration time significantly compared with its closed-loop counterpart. The dual-loop PLL architecture is adopted to achieve a process-independent damping factor and pole-zero separation. A new phase frequency detector embedded with a level shifter is introduced. Careful power partitioning is explored to minimize the noise coupling. The proposed PLL achieves 3. lps RMS jitter running at 1.6GHz while consuming only 0.94mA.
