Adaptive-bandwidth mixing PLL/DLL based multi-phase clock generator for optimal jitter performance

This paper presents an adaptive-bandwidth mixing PLL/DLL (MX-PDLL) based multi-phase clock generator that can operate as a PLL, DLL, or a mixture of the two. Moreover, this clock generator can be used in a proposed dual-loop CDR to minimize output clock jitter under various noise environments. A test-chip prototype of the MX-PDLL and a 360deg phase rotator was fabricated in a 0.18mum CMOS process, operating off of a 1.8V supply. Experimentally measured results verify that while PLL-mode operation offers the ability to better filter quantization noise from the digital CDR control, shifting towards DLL-mode operation offers the ability to reduce jitter as the amount of on-chip noise increases