| 摘要 |
PROBLEM TO BE SOLVED: To provide a frequency detection circuit that has a simple circuit configuration, can save power and reduce area, and can detect a frequency reliably. SOLUTION: A switched capacitor circuit, where equivalent resistance changes according to the frequency of an input clock signal, and a resistive element are connected in series, a supply voltage is divided by the equivalent resistance of the switched capacitor circuit and the resistance of the resistive element, and the divided voltage is inputted to a Schmitt circuit. The Schmitt circuit outputs a high-potential signal when the inputted voltage-divided potential exceeds threshold potential, and outputs a low-potential signal when the inputted voltage-divided potential is less than the threshold potential, thus outputting a high-potential signal or a low-potential signal according to the frequency of an input clock signal and detecting a frequency. COPYRIGHT: (C)2010,JPO&INPIT |
