Circuit for detecting power supply voltage drop
View Patent ↗Provided is a circuit for detecting power supply voltage drop having a small circuit scale. An NMOS transistor ( 12 ) generates a source voltage based on a voltage obtained by subtracting an absolute value of a threshold voltage and an overdrive voltage from a power supply voltage with reference to the power supply voltage. An NMOS transistor ( 17 ) is turned on/off based on the source voltage of the NMOS transistor ( 12 ). A PMOS transistor ( 15 ) generates a source voltage based on a voltage obtained by adding an absolute value of a threshold voltage and an overdrive voltage to a ground voltage with reference to the ground voltage. A PMOS transistor ( 19 ) is turned on/off based on the source voltage of the PMOS transistor ( 15 ).
1. A circuit for detecting power supply voltage drop, which detects a drop of a power supply voltage, comprising:
a first transistor that is of a first conductive type and generates a source voltage based on a voltage obtained by subtracting an absolute value of a threshold voltage and an overdrive voltage from the power supply voltage with reference to the power supply voltage;
a second transistor that is of the first conductive type and turned on/off based on the source voltage of the first transistor;
a third transistor that is of a second conductive type and generates a source voltage based on a voltage obtained by adding an absolute value of a threshold voltage and an overdrive voltage to a ground voltage with reference to the ground voltage;
a fourth transistor that is of the second conductive type and turned on/off based on the source voltage of the third transistor;
a first constant current circuit that supplies a current to the first transistor;
a second constant current circuit that supplies a current to each of the second transistor and the third transistor; and
a third constant current circuit that supplies a current to the fourth transistor.