摘要 |
PROBLEM TO BE SOLVED: To solve a problem wherein an electric power source undetected signal L is not output to disable a reset of a circuit in a following stage by the signal L, when a voltage having a quick leading-up speed is impressed in a reference voltage circuit where a reference voltage is input into a comparison circuit with a fixed lag time, in an electric power source detecting circuit constituted of an electric power source voltage dividing circuit, a reference voltage circuit and the comparison circuit. SOLUTION: An N or PMOS transistor is arranged between the voltage dividing circuit and the comparison circuit, and a gate voltage is supplied from a threshold element connected to the reference voltage circuit. An OFF-condition is brought when the reference voltage is a threshold value of voltage in the threshold element or less, and an ON-condition is brought when exceeding the threshold value. A capacitor is provided in an input side of the comparison circuit, and a resistance inside the voltage dividing circuit and the capacitor constitute an integrated circuit to output an electric power source detection signal H surely, when the transistor is turned on. A diode is inserted to release a charge in the capacitor during an OFF-period, so as to effectuated as measures for a stable operation. COPYRIGHT: (C)2005,JPO&NCIPI
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