Oscillation Frequencies by Output Resistance in a CMOS Quartz Crystal Oscillation Circuit for a Wrist Watch

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  • 時計用CMOS水晶発振回路の出力抵抗による発振周波数
  • トケイヨウ CMOS スイショウ ハッシン カイロ ノ シュツリョク テイコウ

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This paper describes the oscillation frequencies by output resistance in a CMOS quartz crystal oscillation circuit for a wrist watch. A tuning fork type quartz crystal resonator with the frequency of 32.768 kHz is used for wrist watches, because this resonator has advantages of low frequency(low power consumption), miniaturization, high shock-resistance and the existing zero temperature coefficient. However, the resonator vibrates in unwanted spurious modes by the conditions of various constants in a CMOS quartz crystal oscillation circuit, because there exsist unwanted spurios vibrations to be excited by the same electrode. The object of this paper is to suppress the unwanted spurious vibrations, particularly the second overtone vibration. As a result of this study, it is understood that the output resistance suppresses the overtone vibrations, because it changes the retured ratios of each mode. Namely, in this paper, the returned ratios in the quartz crystal oscillation circuit are derived as a function of equivalent electrical constants for a quartz crystal resonator, and the relationship between the returned ratios and the output resistance is made clear.

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