Phase-Locked Loop Circuit with Accelerated Frequency Acquisition

摘要

Frequency acquisition is accelerated in a phase-locked loop circuit. A duration of time for sinking current from or sourcing current to a loop filter is calculated in order to accelerate frequency acquisition of a reference frequency of a reference signal and a feedback frequency of a feedback signal fed back from a controlled oscillator when the feedback signal frequency is changed or frequency of the reference signal is changed by a predetermined amount. The feedback signal frequency is changed or frequency of the reference signal is changed by the predetermined amount. Sinking current from or sourcing current to a loop filter electrically connected to the controlled oscillator for the duration of time is performed resulting in the reduction of the time for frequency acquisition.