A/D CONVERTER AND A/D CONVERTING METHOD

摘要

An A/D converter comprises a plurality of comparators each of which compares an analog input signal with an analog threshold value; a higher-order field deciding part; and a lower-order field deciding part. In a higher-order decision phase, the higher-order field deciding part supplies, to the plurality of comparators in parallel, the respective ones of a plurality of analog threshold values representative of the boundaries of ranges corresponding to data values that may be exhibited by an higher-order field having a predetermined number of bits in a digital output signal. The higher-order field deciding part further determines, based on comparison results of the plurality of comparators, to which range an analog input signal belongs. The higher-order field deciding part then limits the data values of the higher-order field to the data values corresponding to a range between the maximum analog threshold value that is equal to or lower than the analog input signal and the minimum analog threshold value that is equal to or higher than the analog input signal. In a lower-order decision phase, the lower-order field deciding part decides, based on the comparison results of the plurality of comparators, values of bits to be converted.