A pulse modulator receives an analog voltage VIN, and generates a pulse signal that is modulated according to the analog voltage VIN. An output stage generates a switching signal at an output terminal according to the pulse signal. A semiconductor integrated circuit is switchable between (i) a normal mode in which a main signal VMAIN to be used in a normal operating mode is input as the analog voltage VIN to the pulse modulator, and (ii) a test mode in which at least one internal analog signal VAUX generated in the semiconductor integrated circuit is input as the analog voltage VIN to the pulse modulator.