10–315-MHz Cascaded Hybrid Phase-Locked Loop for Pixel Clock Generation

Abstract

A cascaded hybrid phase-locked loop (PLL) fabricated in a 65-nm CMOS process consumes 21 mW and occupies 0.4 mm2. An all-digital PLL (ADPLL) with piecewise linear calibrated hierarchical time-to-digital converter is proposed to achieve a wide operation range, and a charge-pump PLL (CPPLL) with an auxiliary (AUX) charge-pump for low current mismatch is cascaded to filter out the ADPLL output noise. The ADPLL achieves low long-term jitter regardless of the leakage current, and the CPPLL realizes low short-term jitter using a self-biased technique and the AUX charge pump. A phase-selectable divider is also proposed to divide the clock frequency while keeping the relative phase difference constant. The measured peak-to-peak short-term and long-term jitters at an output frequency of 315 MHz are 40 and 70 pspp, respectively, with a multiplication factor of 1024.