Patent ID: 7486151

Claim:
A semiconductor circuit comprising: a current source that is driven by a power supply voltage, said current source outputting a current dependent on the power supply voltage, and said current source outputting a reference voltage as obtained when the power supply voltage is dropped by a predetermined drop voltage, wherein said current source comprises: a current mirror circuit including a first P channel MOSFET and a second P channel MOSFET, a first resistors, and a second resistor, wherein said first P channel MOSFET and said first resistor are interposed between the power supply voltage and a ground, wherein said current source outputs as the reference voltage, an output voltage across said first resistor that is a voltage as obtained when the power supply voltage is dropped by a threshold voltage of said first P channel MOSFET, and wherein said current source outputs the current flowing from the power supply voltage to said capacitor via said second P channel MOSFET and said second resistor; a capacitor that is charged with electric charges by the current outputted from said current source; and a comparator for comparing a voltage across said capacitor with the reference voltage outputted from said current source, and for outputting an output signal when a voltage across said capacitor is equal to or higher than the reference voltage, wherein the semiconductor circuit constitutes a timer circuit that outputs an output signal after a delay time that is equal to such a time as, from a timing when supply of the power supply voltage is started, to a timing when the voltage across said capacitor rises substantially in proportion to an elapsed time by charging said capacitor and reaches the reference voltage.