DIGITAL PHASE LOCKED LOOP CIRCUIT ADJUSTING DIGITAL GAIN TO MAINTAIN LOOP BANDWIDTH UNIFORMLY

摘要

A digital phase locked loop circuit includes a phase frequency detector, a bandwidth calibrator, a digital loop filter, and a digital controlled oscillator. The phase frequency detector generates a first detection value and a second detection value of which each is associated with order between a phase of a reference signal and a phase of a fed-back signal. The bandwidth calibrator amplifies a signal level of the second detection value by a gain value to generate an amplified detection value, and adjusts the gain value based on the first detection value. The digital loop filter generates a digital code based on the amplified detection value. The digital controlled oscillator generates an output signal having a frequency which corresponds to the digital code. The fed-back signal is generated based on the output signal and is fed back to the phase frequency detector.