Abstract: A low voltage detector is provided which detects whether a power supply voltage falls below a predetermined threshold voltage. In accordance with the present invention, the low voltage detector is enabled or disabled with an operating state of a microcontroller. If the microcontroller enters into a halt mode in which the microcontroller does not operate, current flowing to the low voltage detector is cut off. During the halt mode of the microcontroller, the low voltage detector does not consume power, thereby reducing overall power consumption.