RATIO ANALOG-TO-DIGITAL CONVERTER CORRECTING NON-RATIO OFFSET

摘要

PURPOSE: To provide a ratio A/D converter by subtracting a non-ratio offset, stored in a storage device from a digital output, in order to eliminate an offset before calculation of a ratio of an A/D converter so as to cancel a non-ratio error of the A/D converter. CONSTITUTION: This ratio A/D converter 20 generates a digital output DOUT and gives it to a non-inverting input of a non-ratio error offset block 28. An offset stored in a storage device 30 is fed to an inverting input of a ratio offset block 28. The offsets are used to cancel an error from the digital output DOUT of the ratio A/D converter 20, and a value without an error is outputted with respect to the non-ratio offset. This value is given to a system calibration block 32 that conducts system calibration. Thus, the non-ratio offset is obtained at first and then stored in the storage device 30 and subtracted from the digital output DOUT of the A/D converter 20 before compensation of the system gain and the ratio offset.