To obtain each stable A/D conversion value from both A/D converters, when sampling an A/D conversion value in a short period from one A/D converter and sampling an A/D conversion value in a long period from the other A/D converter by using a power supply voltage in common.

Both the A/D converter 1 for sampling the A/D conversion value in the short period and the A/D converter 2 for sampling the A/D conversion value in the long period are set in a constant operation state (continuous conversion mode). Hereby, the total current consumption Ia determined by adding a current consumption Ia1 of the A/D converter 1 to a current consumption Ia2 of the A/D converter 2 becomes constant, to thereby stabilize the power supply voltage Vcc, and a stable A/D conversion value can be obtained from each of the A/D converters.