| 摘要 |
PURPOSE:To use a titled circuit as a crystal oscillator and a CR oscillator by simply changing an externally mounted circuit, by providing a crystal oscillation circuit in parallel with the CR oscillator and switching the oscillation into the CR oscillation when a power supply voltage becomes lower than the hold voltage of the crystal oscillation. CONSTITUTION:A phase inverting circuit I6 is connected in series with a Schmitt circuit consisting of NOR-1, NOR-2 and a phase inverting circuit I15, and a resistor R3 is connected in parallel with the Schmitt circuit, an input terminal TIN is grounded with a capacitor C4 to form a CR oscillation circuit. The CR oscillation circuit is provided with a crystal (or ceramic) oscillator Q, and a capacitor C5 is provided at an output terminal Tout side. The mode is controlled that the crystal (ceramic) oscillation is performed when the power supply voltage is set at a hold voltage or more of the crestal (or ceramic), and the oscillation goes to the CR oscillation, through the stopping of the crystal (ceramic) oscillation and forming of an integrator consisting of the inverting circuit I6, the resistor R3 and the capacitor C4, when the voltage is lower than the hold voltage. |
