Patent ID: 7579973
Filing Date: 2009-08-25
Classification: H03M

Abstract:
1. An analog-digital (A-D) converter for outputting a digital signal corresponding to an analog input signal, comprising: an upper bit A-D converting section for conducting A-D conversion of the analog input signal and outputting an upper bit portion of the digital signal; a lower bit A-D converting section for conducting A-D conversion of the analog input signal and outputting a lower bit portion of the digital signal; a majority circuit for sampling an A-D conversion result of the lower bit A-D converting section a plurality of times and determining a value of each of the lower bits by majority operation; and a variable resistor circuit having a resistance value varying according to digital data for producing a reference voltage, the digital data for producing a reference voltage being produced by adding lower bits having a value “1” to the upper bits, wherein the variable resistor circuit divides a voltage obtained by D-A conversion of the digital data for producing a reference voltage, and the lower bit A-D converting section uses the voltage output from the variable resistor circuit as a reference voltage.