Ad converter and ad conversion method

An AD (Analog/Digital) converter of a successive approximation type configured to perform a sampling process and a successive approximation process on an analog signal, execute an AD conversion process, and output an AD conversion result, the AD converter comprising:

• a DA (Digital/Analog) converter configured to generate a comparison voltage;
• a reference voltage generation circuit configured to generate a reference voltage used for the successive approximation process;
• a comparator configured to compare the comparison voltage with the reference voltage and output a successive approximation result;
• a successive approximation processing unit configured to generate the successive approximation control signal based on the successive approximation result, and to output the AD conversion result;
• and at least one storage unit configured to store an expected value of the AD conversion process based on the AD conversion result, wherein the reference voltage generation circuit generates the reference voltage based on the expected value stored in the storage unit, wherein the AD converter performs the AD conversion process a plurality of N times in succession, where N is an integer greater than or equal to 3,
• wherein the storage unit stores, as the expected value, the AD conversion result of the AD conversion process preceding an (N−1)th AD conversion process as the expected value, and wherein when an Nth AD conversion process is performed, the reference voltage generation circuit uses, as the reference voltage, the AD conversion result of the AD conversion process preceding the (N−1)th AD conversion,
• wherein the expected value stored in the storage unit is updated every time the AD conversion result is output.