A novel multi-reference capacitor switching scheme for ultra-low power successive approximation register (SAR) ADCs is proposed. By using 5 references, the proposed switching scheme only dissipates 10.6 CV²_REF average energy and requires 256 unit capacitors, which are reduced by 99.2% and 87.5%, compared to the conventional structure. Besides, the common-mode voltage of the comparator input is approximately constant, which relaxes the required comparator’s performance. Behavioral simulation results demonstrate the superiority of the proposed switching scheme.