Multi-step extended-counting analogue-to-digital converters

Extended-counting A/D converters are proposed which achieve a high accuracy by performing the conversion in several cycles. During the first cycle, the circuit performs as an incremental ADC, while during the remaining ones it acts as a multi-slope counting converter. With only one opamp and a single-slope ADC, the accuracy is comparable to that of a second-order incremental ADC. A three-step A/D converter using only a single opamp and a two-slope ADC achieves an accuracy comparable to that of a third-order incremental ADC, but with much higher power efficiency.