An 11-Bit 250-nW 10-kS/s SAR ADC With Doubled Input Range for Biomedical Applications

This paper presents a low-power, area-efficient 11-b single-ended successive-approximation-register (SAR) analog-todigital converter (ADC) targeted for biomedical applications. The design features an energy-efficient switching technique with an error cancelling capacitor network. The input range is twice the reference voltage. The ADC's loading of the previous stage is reduced by using a single-ended structure, and by eliminating the largest capacitor in the array. The common mode voltage of the input signal can be used as reference voltage. All building blocks were designed in subthreshold for power efficiency, with an asynchronous self-controlled SAR logic. The ADC was fabricated in 0.18 -μm CMOS 2P4M process. The measured peak SNDR was 60.5 dB, the SFDR was 72 dB, the DNL +0.6/-0.37 LSB, and the INL +0.94/-0.89 LSB. The total power consumption was 250 nW from 0.75-V supply voltage.