| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a phase locked loop (PLL) circuit capable of easily recovering from a runaway state to normal operation. <P>SOLUTION: If it is detected by a comparison section 140 that a control voltage Vcntl exceeds an upper limit voltage value Vref1, an instruction signal switching section 150 supplies to a control voltage generating section 130 another instruction signal (an instruction signal Vu2 for a ground voltage, an instruction signal Vd2 for a power supply voltage) for forcibly dropping the control voltage Vcntl, and the control voltage generating section 130. When it is detected by a comparison section 141 that the control voltage Vcntl becomes lower than a lower limit voltage value Vref2, the instruction signal switching section 150 switches supply to the control voltage generating section 130 from the other instruction signal to an instruction signal from a phase comparator (UP signal Vu1, DOWN signal Vd1) and in accordance with the instruction signal, the control voltage generating section 130 generates the control voltage Vcntl. A voltage controlled oscillation circuit 110 controls an oscillation frequency in accordance with the control voltage Vcntl. <P>COPYRIGHT: (C)2009,JPO&INPIT |
