Patent ID: 7026972

Claim:
An A/D converter comprising: a ramp-wave generation circuit that generates a ramp-wave voltage which steps up or down at a certain gradient; a reference voltage generation circuit that produces a first reference voltage and a second reference voltage; a voltage-to-time conversion circuit that compares the ramp-wave voltage with each of the first reference voltage, second reference voltage, and an input voltage that is an object of conversion, and produces times which the first reference voltage, second reference voltage, and input voltage require for having a predetermined relationship to the ramp-wave voltage; an encoder circuit that converts the three times produced by the voltage-to-time conversion circuit into coded data items proportional to the times; and an arithmetic and logic circuit that fits the coded data, into which the time required by the input voltage is converted by the encoder circuit, to a conversion characteristic curve determined based on the coded data items, into which the times required by the first and second reference voltages are converted by the encoder circuit, and A/D-converted values predefined for the first and second reference voltages, and thus calculates the A/D-converted value of the input voltage.