| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a phase synchronization circuit which can be regulated automatically to satisfy desired characteristics regardless of variation in process or environment. <P>SOLUTION: The phase synchronization circuit comprises a phase frequency comparator 1, a charge pump 2, a loop filter 3, a frequency divider 6, a selector 7, and a voltage controlled oscillator 8. The frequency divider 6 receives an output signal and a reference signal, outputs a feedback signal by dividing frequency of the output signal and outputs a select signal, a trimming signal and a limit signal from the output signal. The voltage controlled oscillator 8 receives a control voltage, a reference voltage, the trimming signal and the limit signal and varies the frequency of the output signal depending on the control voltage. The voltage controlled oscillator 8 can limit the upper limit frequency of the output signal, can vary the frequency sensitivity of the output signal for the control voltage by the trimming signal, and can vary the upper limit frequency of the output signal by the limit signal. <P>COPYRIGHT: (C)2009,JPO&INPIT |
