A 389μm² 26.7nW 8-bit 100kS/s SAR ADC with Hybrid C-CI DAC

An ultra-low power and tiny 8-bit SAR analogto-digital converter (ADC) for biomedical applications is proposed. The proposed SAR ADC introduces a hybrid capacitive-charge injection DAC (C-CI DAC) structure to achieve both high power efficiency and small area. Several methods to minimize the leakage current are used to reduce the power dissipation of the ADC operating at a low clock speed. The proposed C-CI SAR ADC is fabricated in a 28-nm CMOS process and operates from a 0.4-V supply voltage. At a sampling rate of 100 kS/s, the SNDR is 42.57 dB and the power consumption is 26.71 nW. The Walden FOM is 2.43 fJ/convstep and a core area of 389 um<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is achieved.