This paper describes an algorithm for Successive Approximation Register (SAR) ADCs with overlapping steps that allow comparison decision errors (due to, such as DAC incomplete settling) to be digitally corrected. We generalize this non-binary search algorithm, and clarify which decision errors it can digitally correct. This algorithm requires more SAR ADC conversion steps than a binary search algorithm, but we show that the sampling speed of an SAR ADC using this algorithm can be faster than that of a conventional binary-search SAR ADC-because the latter must wait for the settling time of the DAC inside the SAR ADC.
In this paper, a robust cyclic ADC architecture with βencoder is proposed and circuit scheme using switched-capacitor (SC) circuit is introduced. Different from the conventional binary ADC, the redundancy of proposed cyclic ADC outputs β-expansion code and has an advantage of error correction. This feature makes ADC robust against the offset of comparator capacitor mismatch and finite DC gain of amplifier in multiplying-DAC (MDAC). Because the power penalty of high-gain wideband amplifier and the required accuracy of circuit elements for high resolution ADC can be relaxed, the proposed architecture is suitable for deep submicron CMOS technologies beyond 90 nm. We also propose a β-value estimation algorithm to realize high accuracy ADC based on β-expansion. The simulation results show the effectiveness of proposed architecture and robustness of β-encoder.
A β-encoder, a non-binary analog-to-digital converter that is based on the βexpansion, is reported to be robust to large process variations and widespread environment fluctuations. However, the quantization error of the β-encoder is complicatedly distributed and hard to be estimated due to the chaotic nature of the β-transformation. In this work, we propose an analysis method for determining an upper bound of the mean squared error of the quantization. We also provide an evaluation of the signal-to-quantization-noise ratio, which is useful for designing β-encoders.
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