DIGITAL PLL(PHASE LOCKED LOOP) FOR HAVING CONSTANT JITTER CHARACTERISTICS INSENSITIVE TO OPERATING CIRCUMSTANCES

摘要

PURPOSE: A digital PLL(Phase Locked Loop) for having constant jitter characteristics insensitive to operating circumstances is provided to offset the change of total loop-dynamics according to the change of DCO(Digital Controlled Oscillator) characteristics by controlling a coefficient value of a digital loop filter.;CONSTITUTION: A digital PLL(Phase-Locked Loop) includes a digital converter(10), a DLF(Digital Loop Filter)(20), and a digital controlled oscillator(30). A digital TDC(Time-to-Digital Converter) performs the same function as a detector in an analog PLL. The digital converter outputs a digital signal in proportional to the phase difference and frequency difference between an output clock of a reference input clock and a first frequency divider(40). The DLF outputs a controlled control value to the digital controlled oscillator. The digital controlled oscillator generates an output clock.;COPYRIGHT KIPO 2012