A-d converter and a-d convert method

Abstract

An A-D converter includes a plurality of comparators, each of which compares an analog input signal to analog threshold values; an upper field determination section which, during an upper determination phase, supplies in parallel to each of the plurality of comparators the plurality of analog threshold values expressing boundaries of ranges corresponding to each data value acquired from the upper field of a number of bits previously designated in the digital output signal, detects whether the analog input signal is associated with one of the ranges based on comparison results by the plurality of comparators, and narrows data values of the upper field to data values corresponding to a range between the largest analog threshold value less than or equal to the analog input signal and the smallest analog threshold value greater than or equal to the analog input signal; and a lower field determination section which, during the lower determination phase, determines values of conversion target bits based on a plurality of comparison results of the plurality of comparators.