US Patent 7639169 A/D converter circuit and A/D conversion method

An A/D converter circuit has a first ring delay line and a second ring delay line configured to vary respective characteristics in the same manner relative to a change in the ambient temperature. A reference voltage, which is free from a change in temperature, is fed as a power supply voltage to the second ring delay line. Digital data produced by the first ring delay line is temperature-compensated by digital data produced by the second ring delay line.