An extended radix-based digital calibration technique for multi-stage ADC

A radix-based digital self-calibration technique for multi-stage analog-to-digital converter (ADC) is presented. This technique can correct errors due to capacitor mismatch and finite opamp gain. The equivalent radix of each stage is extracted by measuring the discontinuity on the ADC transfer curve and iteratively adjusting the equivalent radix to minimize this discontinuity. A much more accurate analog to digital conversion can be achieved by calculating the digital output based on these equivalent radices. While the principle is very similar to a method described previously, this technique can be applied to those ADCs having multiplying-digital-to-analog-converter (MDAC) with more widely used "capacitor-flip-over" structure. This can be seen as an extension to the previous method.