Patent ID: 9608659
Date: 2017-03-28
CPC Classifications: H03M

Claim:
1. An A/D conversion circuit for outputting A/D conversion data in accordance with a difference between an analog input voltage and a reference voltage, the A/D conversion circuit comprising: a first pulse circulation circuit and a second pulse circulation circuit, each of which is provided by a plurality of delay units for delaying an input signal by a delay time that is determined in accordance with a power source voltage and for outputting a delayed input signal, and circulates a pulse signal through the delay units, the delay units being connected to each other in a ring shape; a circulation number difference measurement section that counts the number of circulation times of the pulse signal through the first pulse circulation circuit and the number of circulation times of the pulse signal through the second pulse circulation circuit, and outputs a differential value between counted numbers; a conversion control circuit that outputs a conversion data output processing signal for determining a timing to complete A/D conversion, and outputs the differential value outputted by the circulation number difference measurement section as A/D conversion data with respect to the analog input voltage; and a signal ratio change circuit that: each delay unit of the first pulse circulation circuit receives a power source voltage supplied from the first output terminal of the signal ratio change circuit and a ground line; and each delay unit of the second pulse circulation circuit receives a power source voltage supplied from the second output terminal of the signal ratio change circuit and the ground line.