A 10b SAR ADC with an Ultra-Low Power Supply

A 0.2V 10-bit 5 kS/s Successive Approximation Register ADC design is presented. This design achieves a very low power consumption due to the ultra-low power supply voltage used. Different aspects in the ADC design are optimized for 0.2V and modified to meet the speed requirements for the ADC. Preliminary Cadence simulations show a 4nW total power consumption with a peak SNDR of 57 dB and a FOM of 1.3 fJ/conversion-step

Ultra-Low Power ADCs for Space Sensors and Instruments

A 28nm 0.1V 10-bit 2kS/s Successive Approximation Register ADC design is proposed. This design opens the doors to both low supply and low power space sensors and instruments. Due to the stringent voltage supply unique challenges arise that are met with innovation in the sample switch and comparator design. These components of the ADC architecture are optimized to perform successfully at a 0.1V supply with a sample rate suitable for most sensor applications

A 10-bit SAR ADC with an Ultra-Low Power Supply

This paper presents a successive approximation analog-to-digital converter (SAR ADC) design, which operates with a 0.2 V power supply. The design utilizes a dynamic bulk biasing scheme to dynamically adjust the relative NMOS and PMOS strengths, which are very sensitive to temperature, process, and mismatch variations at low supply voltages. The design achieves a very low power consumption due to the 0.2 V supply. Several circuits in the design are optimized for full functionality at 0.2 V. Extracted simulations show a total power consumption of 9 nW with a peak SNDR of 61.3 dB and a Walden Figure of Merit of 1.91 fJ/conversion-step

NOISE SHAPING IN SAR ADC

The successive approximation register (SAR) analog-to-digital converter (ADC) is currently the most popular type of ADC architecture, owing to its power efficiency. They are also used in multichannel systems, where power efficiency is of high importance because of the large number of simultaneously working channels. However, the SAR ADC architecture is not the most area efficient. In SAR ADCs, the binary weighted capacitive digital-to-analog converter (DAC) is used, which means that one additional bit of resolution costs double the increase of area. Oversampling and noise shaping are methods that allow an increase in resolution without an increase of area. In this paper we present the new SAR ADC architectures with a noise shaping. A first-order noise transfer function (NTF) with zero located nearly at one can be achieved. We propose two modifications of the architecture: with zero-only NTF and with the NTF with additional pole. The additional pole theoretically increases the efficiency of noise shaping to further 3 dB. The architectures were applied to the design of SAR ADCs in a 65 nm complementary metal-oxide semiconductor (CMOS) with OSR equal to 10. A 6-bit capacitive DAC was used. The proposed  architectures  provide nearly 4 additional bits in ENOB. The equalent input bandwitdth is equal to 200 kHz with the sampling rate equal to 4 MS/s

A fully integrated RSSI and an ultra-low power SAR ADC for 5.8 GHz DSRC ETC transceiver

This study presents a monolithic received signal strength indicator (RSSI) and an ultra-low power SAR ADC for 5.8 GHz DSRC transceiver in China electronic toll collection systems. In order to meet the stringent requirement of wide input range for the transceiver, two RSSIs collaborate with auxiliary ADC circuits to provide the digitalized received signal strength to the digital baseband of a transceiver. The RSSI design achieves fast transient response and low power consumption with a small die area by using internal active low-pass filters instead of external passive ones. The proposed design has been fabricated using a 0.13 μm 2P6M CMOS technology. Measurement results show that the overall input dynamic range is 86 dB with an accuracy of ±1.72 dB and a transient response of less than 2 μs. Compared with the state-of-the-art designs in the literature, the overall input range and transient settling time are improved by at least 14.6%, and 300%, respectively

Analysis and study of powerefficient sar adc for active rfid sensor

This thesis introduced an energy-efficient successive-approximation-register (SAR) analog-to-digital converter (ADC) specialized to the active sensors for low-power radio frequency identification (RFID) tag system. As part of the Internet of Things (IoT) transformation, RFID is widely used. In the application where the power supply is limited, power consumption is always a notable criterion as analog circuits such as the ADC circuit, regulator circuit, rectifier circuit and radio frequency (RF) are the common power demanding parts in the system. Normally, the requirement for a longer battery performance is closely related to low-power consumption. For the application active RFID sensor in which requires low to moderate resolution and speed as well as low-power consumption, SAR is usually used as its part of the ADC circuit. Therefore, the power-efficient SAR ADC is presented in this work. The block of SAR ADCs such as the comparator block, digital-to-analog converter (DAC) block, and sampler block is designed to meet the requirement of a low-power consumption performance measurement. This thesis at first will explores the differences between multiple ADC techniques in the previous works. The proposed SAR ADC is presented to enhance the power consumption of SAR ADC in the active RFID sensor application through the implementation of a single-input comparator with the switched-capacitor DAC. In this form of architecture, there is only one input to the comparator, and only one set and a split sampling capacitor in the switched capacitor DAC to generate the required reference levels. The difference in input and output voltage of the proposed SAR ADC is the indication for the low-power design. The influence of parasitic capacitance is reduced to the extent of becoming a non-factor. The parameters of the SAR ADC are the resolution of 8-bit, the sampling frequency of 500 kHz, the supply voltage of 1 V, and the 0.18 μm complementary metal-oxide-semiconductor (CMOS) technology. The power consumption of the proposed SAR ADC is 2.3 μW which is estimated at around 25.8% improvement from the previous work. The demands for low-power consumption of RFID active sensor is well examined. The validity of the proposed design has been proven by the simulation results

Capacitance-to-Digital Converter for Ultra-Low-Power Wireless Sensor Nodes

Power consumption is one of the main design constraints in today’s integrated circuits. For systems like wearable electronics, UAVs, IOT systems powered by batteries which are charged using the energy harvested from various sources like RF, Thermal, Solar and Vibration, ultra-low power consumption is paramount. In these systems, Transducers which convert physical parameters into electrical parameters and the analog-to-digital converters (ADCs) are key components as the interface between the analog world and the digital domain. This thesis addresses the design challenges, strategies, as well as circuit techniques of ultra-low-power signal Front End used in several low power electronic systems in general and pressure measurement systems in particular. In this thesis, Capacitance to Digital Converter based pressure measurement system has been implemented. Here we present a general-purpose, wide-range CDC that combines a correlated double sampling (CDS) approach with a differential asynchronous SAR ADC. Since the sensor capacitor is sampled only twice per conversion, energy per conversion is low. Furthermore, since the CDS separates the sensor capacitor from the CDAC, a full differential input voltage range is preserved. The CDC has a 2.5-to-75.5pF conversion range. Monotonic SAR ADC was designed in 180nm CMOS with 1-V power supply and a 1-kS/s sampling rate with switching energy of about 100nW

A two-dimension time-domain comparator for low power SAR ADCs

This paper presents a two-dimension time-domain comparator suitable for low power successive-approximation register (SAR) analog-to-digital converters (ADCs). The proposed two-dimension time-domain comparator consists of a ring oscillator collapse-based comparator and a counter. The propagation delay of a voltage controlled ring oscillator depends on the input. Thus, the comparator can automatically change the comparison time according to its input difference, which can adjust the power consumption of the comparator dynamically without any control logic. And a counter is utilized to count the cycle needed to finish a comparison when the input difference is small. Thus, the proposed comparator can not only provide the polarity of the input, but also the amount information of the input, which helps to skip most of the SAR cycles when the initial input is small. Thus, most energy can be saved when the initial input is small. The proposed time-domain comparator is designed in 0.18 μm CMOS technology. Simulation results demonstrate that the comparator can not only save power consumption, but also give the design flexibility, and the current is only nA level when the supply voltage is 0.6 V.National Natural Science Foundation of China under grant No. 61704015; General program of Chongqing Natural Science Foundation (a special program for the fundamental and frontier research) under grant No. cstc2019jcyj-msxmX0108