A High-Energy Dual-CDAC Single-Capacitor Switching Strategy Applied to SAR ADC

An ultra-low power dual-CDAC switching strategy applied in SAR ADC is proposed. This switching scheme adopts two sub-CDAC structures. The first CDAC switching adopts the CDAC selection mode, and the subsequent first conversion adopts the overall reference voltage switching to realize the maximum two-bit quantization without power consumption. The subsequent switch only involves the capacitance in a single position of a single CDAC, which is simpler to switch, and the capacitance ratio on each CDAC is reduced by using a dual CDAC. The total capacitance is reduced from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2^{N-1}$</tex> to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2^{N-2}$</tex>, and the use of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_{cm}$</tex> as the intermediate reference voltage can achieve lower switching power consumption than the existing research literature, and the same unit capacitance under the premise of N-bit resolution requires less total CDAC capacitance, reducing the area overhead. Through numerical simulation analysis, The proposed switching structure is reduced by 97.7<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">%</sup> and area of proposed CDAC structure is optimized by 75%, which compared with traditional CDAC switching.