Enhanced all digital phase-locked loop and oscillation signal generation method thereof

Abstract

An All Digital PLL (ADPLL) and oscillation signal generation method using the ADPLL is provided for generating a spur-free oscillation signal by improving the frequency resolution of the ADPLL. An all digital phase-locked loop of the present invention includes a digitally controlled oscillator for generating an oscillation signal having a frequency corresponding to an inputted control signal, a re-timer for retiming a reference clock based on the oscillation signal, a feedback circuit for accumulating a number of clocks of the oscillation signal within a time period and generating a phase information of the oscillation signal in synchronization with the retimed reference clock, a sigma-delta modulator for sigma-delta modulating a frequency command signal into a modulation signal having a less number of bits than a number of bits of the frequency command signal, a reference phase accumulator for accumulating phases corresponding to the modulation signal, a phase difference detector for generating a phase difference information between an output signal of the reference phase accumulator and the phase information, and a digital loop filter for filtering the phase difference information to generate the control signal.