A/D converter circuit including pulse circulation circuit with delay units coupled together in ring shape

An A/D converter circuit comprising:

• a first pulse circulation circuit configured with a plurality of delay units coupled together in a ring shape and operable to circulate a pulse signal around the delay units, the plural delay units using a difference voltage of a specified voltage and an analog input voltage as a first power supply voltage and outputting an input signal after a delay of a delay time defined in accordance with the first power supply voltage;
• a second pulse circulation circuit configured with a plurality of delay units coupled together in a ring shape and operable to circulate a pulse signal around the delay units, the plural delay units using the analog input voltage as a second power supply voltage and outputting an input signal after a delay of a delay time defined in accordance with the second power supply voltage;
• a first counter operable to count a circulation number of the pulse signal in the first pulse circulation circuit and a circulation number of the pulse signal in the second pulse circulation circuit, and operable to output a difference of the circulation numbers;
• a third pulse circulation circuit configured with a plurality of delay units coupled together in a ring shape and operable to circulate a pulse signal around the delay units, the delay units being supplied with a set voltage different from a reference voltage and using a difference voltage of the specified voltage and the set voltage as a third power supply voltage, and outputting an input signal after a delay of a delay time defined in accordance with the third power supply voltage;
• a fourth pulse circulation circuit configured with a plurality of delay units coupled together in a ring shape and operable to circulate a pulse signal around the delay units, the delay units operating with the use of the set voltage as a fourth power supply voltage and outputting an input signal after a delay of a delay time defined in accordance with the fourth power supply voltage;
• a second counter operable to count the circulation number of the pulse signal in the third pulse circulation circuit and the circulation number of the pulse signal in the fourth pulse circulation circuit, and operable to output a difference of the circulation numbers;
• and
• a conversion control circuit operable to make the first to the fourth pulse circulation circuits start respective circulation operation of the pulse signals concurrently, operable to output a conversion data output process signal when the difference outputted by the second counter reaches a predetermined specified value, and operable to output the difference outputted by the first counter at a time as A/D conversion data corresponding to the analog input voltage,
• wherein the delay units provided in each of the first to the fourth pulse circulation circuits are in the same number and formed in a thermally coupled state with each other.