Phase-locked loop

Abstract

A phase-locked loop is described and has a phase detector that provides at its output per clock cycle a current pulse whose pulse duration is a measure of a phase difference between an input signal and an output signal of the phase-locked loop. A loop filter is connected downstream of the phase detector. The loop filter has a converter device, at least one controllable switching device and at least two switchable capacitive elements for storing a current pulse. In which case the converter device, the switching device and the capacitive elements can be connected up in such a way that the converter device provides a proportional current from a current pulse coupled into at least one of the capacitive elements. An amplitude of the proportional current is constant over the entire length of a clock period. An oscillator is connected downstream of the loop filter, into which oscillator the proportional current can be coupled.