Patent ID: 7315273

Claim:
An analog-to-digital conversion method for converting a difference signal component of an analog signal to be processed including a reference component and a signal component into digital data, the difference signal component representing a difference between the reference component and the signal component, the method comprising the steps of: performing a first process of comparing a signal corresponding to one of the reference component and the signal component with a reference signal for conversion into the digital data, performing counting in one of a down-count mode and an up-count mode concurrently with the comparison, and holding a count value at a time of completion of the comparison; and performing a second process of comparing a signal corresponding to the other one of the reference component and the signal component with the reference signal, performing counting in the other one of the down-count mode and the up-count mode concurrently with the comparison, and holding a count value at a time of completion of the comparison, wherein, the reference signal has the same change characteristics between the first process and the second process.