Patent ID: 7880661

Claim:
An analog-digital converter, comprising: an integrating unit for integrating a difference between a reference voltage and a comparing voltage to output a second voltage, wherein the reference voltage has a zero or positive voltage level and the comparing voltage has a voltage level higher than that of the reference voltage; and a counting unit for counting clocks of a clock signal input thereto until the second voltage reaches a first voltage and outputting a digital code corresponding to a voltage level of the first voltage, wherein the integrating unit includes: an operational amplifier having an inverting terminal and a noninverting terminal for receiving the comparing voltage; a resistor having one end coupled to the inverting terminal of the operational amplifier and the other end coupled to receive the reference voltage; and a capacitor coupled between the inverting terminal and an output terminal of the operational amplifier, wherein the counting unit includes: a comparator for comparing the first voltage with the second voltage; a logic gate for logically combining the clock signal and an output of the comparator; and a counter for counting outputs of the logic gate to output the digital code, wherein the first voltage is a voltage that varies based on a sensed temperature and the second voltage output from the integrating unit increases as time passes.