An All-Digital Despreading Clock Generator

An all-digital despreading clock generator (DSCG) is presented. For an input spread-spectrum clock with a modulation frequency of 15-40 kHz and a down spreading of 5000 ppm, this DSCG successfully realizes a nonspread-spectrum clock. It is fabricated in a 0.18- μm CMOS process. For an input spread-spectrum clock of 1.5 GHz with a down spreading of 5000 ppm and a modulation frequency of 30 kHz, the measured root-mean-square and peak-to-peak jitters of this DSCG are 2.94 and 22.78 ps, respectively. The active area including input/output buffers is 0.84 mm
²
. Its power consumption is 19.8 mW, for a supply of 1.8 V.