| 摘要 |
The invention includes a phase locked loop which has a voltage-controlled oscillator, a phase comparator and a charge pump. The charge pump is coupled to a setting input of the voltage-controlled oscillator via a loop filter. A feedback input of the phase comparator is connected to the output of the voltage-controlled oscillator via a frequency divider, and the phase comparator is designed to output an actuating signal to the charge pump. The loop filter has a first charge store and at least one tunable element that alters a filter characteristic of the loop filter. In addition, there is a trimming circuit which is coupled to the at least one further element in order to alter the filter characteristic of the loop filter and which is designed to compare a time period for a charging operation in a loop filter with a reference time period.
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