A 90MS/s 11MHz bandwidth 62dB SNDR noise-shaping SAR ADC

In recent years, charge-redistribution SAR (Successive Approximation) ADCs have exhibited the highest conversion efficiencies for ADCs with moderate res olution and bandwidth. For effective resolutions beyond 10b or so, however, the accuracy of the SAR circuit blocks limits the overall energy efficiency of the converter. At high resolutions, for instance, the DAC voltages become small compared to the input-referred noise of a dynamic comparator, necessitating an additional power-hungry, low-noise pre-amplifier to drive the comparator. To improve the resolutions of SAR ADCs, this work introduces a technique to decouple the accuracy of the comparator from the resolution of the ADC. In this paper, we introduce a low-OSR (Oversampling Ratio) noise-shaping SAR ADC that leverages noise-shaping to increase the resolution of a conventional SAR ADC.