A WideInput-Range EA\Modulator forApplications toSpread-Spectrum ClockGenerator

A spread-spectrum clockgenerator (SSCG) using fractional-N phase-locked loop(PLL)withanextended rangesigma-delta (1,A) modulator ispresented inthis paper. Theproposed YAmodulator simply addsanextra output bitin thefirst stage modulator. Itcanenlarge theinput rangeabout threetimesascompared totheconventional modulator and solvethesaturation problemwhentheinputexceeds the boundary oftheconventional modulator. Theproposed SSCG hasbeenfabricated inTSMC 0.35-um double-poly quadruple- metalCMOS process withoutput frequency of300MHz.The active areais0.63X0.62 mm2 andthepowerconsumption is 17.5mW.