| 摘要 |
PURPOSE: A frequency detecting circuit is provided to stably output a high level and a low level by setting the high resistance of a switch capacitor and reducing current consumption. CONSTITUTION: A frequency detecting circuit comprises a switch capacitor circuit(2), a resistor(3), and a branch potential detection circuit. The switch capacitor circuit changes the equivalent resistance according to the frequency of the input clock signal. The resistor unit is connected between the switch capacitor circuit and the ground. The branch potential detection circuit detects the branch potential of power supply unit. The branch potential of the power supply voltage unit is divided by the switch capacitor circuit and the resistor unit. If the branch potential is over than threshold potential, the branch potential of the power supply voltage unit outputs high potential signal, and if not, the branch potential of the power supply voltage unit outputs low potential signal.
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