Patent ID: 8421891

Claim:
An A/D conversion apparatus for comparing a reference signal with an analog signal, and when the reference signal matches with the analog signal, outputting a corresponding digital value, wherein the A/D conversion apparatus includes a gray code counter for generating the digital value from a reference clock or a reverse clock of the reference clock, and uses a gray code, wherein the digital value includes a count value of the gray code counter, wherein the count value is a value defined as a most significant bit to a third least significant bit of the digital value; a second least significant bit of the digital value is generated from the reference clock or the reverse clock thereof and defined as a second least bit of the gray code counter; and a least significant bit of the digital value is configured with a signal of a same period as that of another reference clock or another reverse clock thereof obtained by deviating one-fourth of a phase of the reference clock or the reverse clock thereof.