Capacitor mismatch plays an important part in the spurious-free dynamic range (SFDR) performance of high-resolution successive approximation register (SAR) analog-to-digital converters (ADCs). This paper presents a symmetric group control dynamic element matching (SGCDEM) method aiming at enhancing SFDR of SAR ADCs applied in biomedical applications. The proposed scheme symmetrically divides the capacitor array into four sub-DACs, using quantization results corresponding to each sub-DAC as rotary control codes to symmetrically control the rotation of the capacitors. In order to improve the energy efficiency and save chip area, the proposed method replaces the pseudo-random number generator (PRNG) with quantization results of ADC as the rotary control code. Moreover, split rotator technology is applied in the proposed scheme to reduce the number of multiplexers (MUX) used in the rotator, which introduces a low logic depth. The proposed architecture has been implemented on a 12-bit SAR ADC model in MATLAB in order to verify its performances. After taking a standard deviation of 1% for the unit capacitance into consideration, this method achieves above 77.3dB SFDR, enabling to correct the SFDR by more than 23.6dB compared with the structure without DEM.

中文翻译：

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一种应用于生物医学应用的高分辨率 SAR ADC 的对称群控制动态元素匹配方法

电容器失配在高分辨率逐次逼近寄存器 (SAR) 模数转换器 (ADC) 的无杂散动态范围 (SFDR) 性能中起着重要作用。本文提出了一种对称群控动态元素匹配 (SGCDEM) 方法，旨在提高生物医学应用中 SAR ADC 的 SFDR。所提出的方案将电容器阵列对称地划分为四个子DAC，将每个子DAC对应的量化结果作为旋转控制码来对称地控制电容器的旋转。为了提高能效和节省芯片面积，该方法用ADC的量化结果代替伪随机数发生器（PRNG）作为旋转控制码。而且，在所提出的方案中应用了拆分旋转器技术，以减少旋转器中使用的多路复用器 (MUX) 的数量，这引入了低逻辑深度。所提出的架构已在 MATLAB 中的 12 位 SAR ADC 模型上实现，以验证其性能。考虑单位电容1%的标准偏差后，该方法达到77.3以上dB SFDR，能够将 SFDR 校正超过 23.6dB 与没有 DEM 的结构相比。