A CMOS Fourth-order 14b 500k-sample/s Sigma-delta ADC Converter

The sigma-delta principle allows realization of ND and DIA converters with a high dynamic range in a standard CMOS process without excessive component matching requirements. 1 Accuracy is obtained at the cost of a sampling rate reduction. The speed penalty becomes less severe as the modulator order is increased. However,sigma-delta modulators with order larger than two show stability problems. For some initial conditions of the internal signals, the loop is stable while for other initial conditions, the loop oscillates.