Patent ID: 7626532
Filing Date: 2009-12-01
Classification: H03M,H04N

Abstract:
1. An A/D converter comprising: a ramp voltage generation circuit generating a ramp voltage having a voltage value changing monotonically for a certain period; a voltage comparison circuit comprising an arithmetic unit sampling and holding an analog voltage to be converted and comparing the sampled and held analog voltage to be converted, with a reference voltage given by a voltage change value of the ramp voltage generated from the ramp voltage generation circuit or a voltage value proportional to the voltage change value, and changing an output when the reference voltage equals the analog voltage to be converted; a counter counting a digital value corresponding to the reference voltage and outputting the digital value; a latch circuit latching the digital value outputted from the counter when the output of the voltage comparison circuit is changed and outputting the digital value; an averaging process circuit averaging a noise component contained in the analog voltage to be converted to obtain an average noise voltage; a target noise voltage setting circuit setting a target noise voltage as a target value of the average noise voltage; and a control circuit performing at least one adjustment of a counting start timing of the counter with respect to a control reference timing at which the reference voltage starts to change from a criterion level by the ramp voltage generation circuit, or adjustment of the criterion level of the reference voltage at the counting start timing of the counter, based on a difference between the average noise voltage and the target noise voltage.