A semiconductor integrated circuit according to an embodiment includes an oscillator that generates and outputs an oscillation signal in an active state and generates no oscillation signal in an inactive state. The semiconductor integrated circuit includes a negative charge pump that generates an output voltage that is a negative voltage in response to the oscillation signal and outputs the output voltage to an output pad. The semiconductor integrated circuit includes a negative voltage detecting circuit that detects the output voltage and controls the oscillator to be in the active state or inactive state so as to bring the output voltage close to a target voltage.