Patent ID: 7180344

Claim:
A phase locked loop, comprising: a voltage-controlled oscillator comprising a setting input and with a signal output that forms a control loop output from the phase locked loop; a phase comparator comprising a reference input configured to receive a reference signal, a feedback input connected to the signal output of the voltage-controlled oscillator via a frequency divider to form a feedback path, and an output, and configured to output an actuating signal at the output thereof based on a comparison of a feedback path signal and the reference signal; a charge pump configured to output a control voltage derived from the actuating signal, the charge pump comprising a control input connected to the output of the phase comparator; a loop filter comprising an output coupled to the setting input of the voltage-controlled oscillator and an input configured to receive the control voltage from the charge pump, and comprising a first charge store and at least one tunable element configured to selectively alter a filter characteristic of the loop filter; and a trimming circuit operably coupled to the loop filter, and configured to compare a time period for at least one charging operation in the first charge store of the loop filter with a reference time period, and configured to selectively tune the at least one tunable element in order to alter the filter characteristic of the loop filter based on the comparison.