A 10-Bit 250-KS/s 1.24-uW SAR ADC for IoT Sensors with Energy-Efficient Comparator.

This paper describes a 10-bit 250-KS/s successive-approximation register (SAR) analog-to-digital converter (ADC) for IoT sensors. In order to reduce the power consumption and the area, the bridge-capacitor array and the top-plate sampling method are used in the digital-to-analog converter (DAC). What's more, the VCM-based switching method is applied while a new energy-efficient comparator is proposed, which relaxes the stringent speed-power trade-off under the 1.2-V supply. The effects of parasitic factors on circuit performance are minimized by the adaptive calibration technique, which introduces a new reference voltage. The flexible reference voltage improves the linearity of the proposed SAR ADC. A prototype implementation in 55nm CMOS exhibits an SNDR of 56.1 dB with the input signal frequency 105 KHz and totally consumes 1.24 uW. The figure of merit (FoM) is 8 fJ/conservation step and the area of the chip is 0.065 mm ² .