Patent ID: 7102395

Claim:
A power-supply voltage detection circuit for detecting that at least one of an external power-supply voltage and an internal power-supply voltage generated from the external power-supply voltage goes out of a predetermined regulation, the circuit comprising: a first comparator comparing a first output voltage with a reference voltage, said first output voltage generated based on the internal power-supply voltage, for detecting the internal power-supply voltage being equal to or less than a first predetermined value; a second comparator comparing a second output voltage with a reference voltage, said second output voltage generated based on the internal power-supply voltage, for detecting the internal power-supply voltage being greater than a second predetermined value; a first capacitor for AC-coupling a first input terminal of the first comparator to the external power-supply voltage; a second capacitor for AC-coupling a first input terminal of the second comparator to the external power-supply voltage; a third capacitor for AC-coupling a second input terminal of the first comparator to the internal power-supply voltage; and a fourth capacitor for AC-coupling a second input terminal of the second comparator to the internal power-supply voltage, wherein an output of the first comparator and an output of the second comparator each provides a signal that indicates that the predetermined regulation has been exceeded.