One A/D converter and the other A/D converter have a common power supply voltage and sample an A/D conversion value at short time intervals and at a long time intervals, respectively. Both the A/D converter and the A/D converter are set in a constant active state (continuous conversion mode). This allows the total consumption current combining the consumption current of the A/D converter and the consumption current of the A/D converter to be constant, so that the power supply voltage is stabilized and a stable A/D conversion value can be obtained from each of the A/D converters.