| 摘要 |
In a phase locked loop circuit, a phase difference signal (an up signal and a down signal) is supplied from a phase comparator to a serial-to-parallel converting circuit, and an output of the serial-to-parallel converting circuit is supplied to an up-down counter having a count value is counted up or down in accordance with the phase difference detected by the phase comparator. A voltage controlled oscillator generates an oscillation signal having the frequency controlled in accordance with the count value of the up-down counter. Thus, since the phase difference signal is serial-to-parallel converted, the rate of the phase difference signal is lowered, so that the operation speed of the up-down counter can be relaxed. Therefore, the operation speed of the phase locked loop circuit can be elevated with elevating the operation speed of the up-down counter.
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