An All-Digital PLL for Video Pixel Clock Regeneration Applications

This paper presents an all-digital PLL (ADPLL) for the pixel clock regeneration in analog video signal digitization applications. A fine frequency resolution, 1-1-1 MASH structure based fractional-N PLL (FN-PLL) is used as the digital-controlled oscillator (DCO). Two loop filters which are triggered by different clock frequencies and both with adaptive gain controllers are combined together working at different states to increase both the tracking speed and the locked jitter performance. The ADPLL maximum output frequency is determined by the FN-PLL's voltage-controlled oscillator (VCO) which can be upper than lGhz. It covers any VESA and HDTV specification requirements even at 4X over-sampling ratio. A test chip contains this ADPLL prototype has been implemented in a 0.13 um CMOS technology. The layout area is about 0.2 mm
²
, the measured RMS jitter is 32.4 ps.