A jitter control circuit within a chip comprises an adaptive PDN, a current generator and a jitter generator. The adaptive PDN is capable of being controlled/modulated to provide difference impedances. The current generator is coupled to the adaptive PDN, and is arranged for receiving a supply voltage provided by the adaptive PDN and generating currents with different patterns. The jitter generator is coupled to the adaptive PDN, and is arranged for generating a plurality of jitters corresponding to the currents with different patterns, respectively, according to the supply voltage provided by the adaptive PDN.