| 摘要 |
PURPOSE: To synchronize the phases of output of high accuracy oscillator and a clock and improve the accuracy of a real time clock by comparing the phase of output of the high accuracy oscillator and the phase of output of the real time clock, converting the result to a direct current voltage and changing the bias of a variable-capacitance diode. CONSTITUTION: In the case the frequency of a Y-cut crystal oscillator 1 deviates to higher side due to temperature change and the like, the output of a frequency divider 10 deviates to more gaining side than the output of a frequency divider 11. As a result, the output voltage of a phase comparison circuit 9 decreases, the capacitance of variable-capacitance diode 4, 5 are increased and the frequency of the crystal oscillator 1 is deviated to lower side. Conversely, when the frequency of the crystal oscillator 1 deviates to lower side, the frequency of the crystal oscillator 1 is deviated to increasing side. This operation is repeated until the output of the crystal oscillator 1 and the output of the high accuracy oscillator 12 synchronize in order to supply a clock with an accuracy equivalent to the high accuracy oscillator 12 and maintain the LSI13 for a real time clock at high accuracy. |
