An 8-bit 166nw 11.25 kS/s 0.18um two-Step-SAR ADC for RFID applications using novel DAC architecture

SAR ADCs have been mostly used for moderate-speed, moderate-resolution applications that power consumption is one of the major concerns (e. g. RFID). Furthermore two-step ADCs are classified as high-speed, low to moderate-accuracy ADC. In this paper an ultra low power two-step-SAR ADC for RFID application is presented. Several techniques are used to further reduce the power consumption and relatively elevate the speed of the ADC. These techniques include a low power comparator with no static current and a dual-stage (Resistor-string / capacitive dividing) architecture as digital-to-analog converter (DAC). In this DAC architecture fine search will be performed by only two C and 15C capacitors which reduced the silicon area significantly. The circuit designed in 0.18um CMOS technology and simulations show that the 8-bit ADC, consumes almost 166nW at 11.25kS/s. The results show that the proposed ADC has higher speed with almost the same power consumption in comparison with its charge redistribution counterpart.