Fully Synthesizable, Rail-to-Rail Dynamic Voltage Comparator for Operation down to 0.3V

A novel rail-to-rail dynamic voltage comparator is presented in this paper. The proposed circuit is fully synthesizable, as it can be designed with automated digital design flows and standard cells, and can operate at very low voltages down to deep sub-threshold. Post-layout simulations show correct operation for rail-to-rail common-mode inputs at a supply voltage VDD down to 0.3 V. At such voltage, the input offset voltage standard deviation is less than 28 mV (8 mV) over the rail-to-rail common-mode input range (around VDD/2). The digital nature of the comparator and its ability to operate down to deep sub-threshold voltages allow its full integration with standard-cell digital circuits in terms of both design and voltage domain. The ease of design, the low area and the voltage scalability make the proposed comparator very well suited for sensor nodes, integrated circuits for the Internet of Things and related applications

All-Standard-Cell-Based Analog-to-Digital Architectures Well-Suited for Internet of Things Applications

SMART-E-PTDC/CTM-PAM/04012/2022, IDS-PAPER-PTDC/CTM-PAM/4241/2020 and PEST (CTS/UNINOVA)-UIDB/00066/2020. This work also received funding from the European Community’s H2020 program [Grant Agreement No. 716510 (ERC-2016-StG TREND) and 952169 (SYNERGY, H2020-WIDESPREAD-2020-5, CSA)]. Publisher Copyright: © 2022 by the authors.In this paper, the most suited analog-to-digital (A/D) converters (ADCs) for Internet of Things (IoT) applications are compared in terms of complexity, dynamic performance, and energy efficiency. Among them, an innovative hybrid topology, a digital–delta (Δ) modulator (ΔM) ADC employing noise shaping (NS), is proposed. To implement the active building blocks, several standard-cell-based synthesizable comparators and amplifiers are examined and compared in terms of their key performance parameters. The simulation results of a fully synthesizable Digital-ΔM with NS using passive and standard-cell-based circuitry show a peak of 72.5 dB in the signal-to-noise and distortion ratio (SNDR) for a 113 kHz input signal and 1 MHz bandwidth (BW). The estimated (Formula presented.) is close to 16.2 fJ/conv.-step.publishersversionpublishe

Design of a Comparator and an Amplifier in CMOS using standard logic gates

Using standard logic gates in CMOS, or standard-cells, has the advantage of full synthe- sizability, as well as the voltage scalability between technologies. In this work a general pur- pose standard-cell-based voltage comparator and amplifier are presented. The objective is to design a general purpose standard-cell-based comparator and ampli- fier in 130 nm CMOS by optimizing the already existing topologies with the aim of improving some of the specifications of the studied topologies. Various simulation testbenches were made to test the studied topologies of comparators and amplifiers, in which the results were compared. The top performing standard-cell com- parator and amplifier were then modified. After successfully designing the comparator, it was used in the design of an opamp-less Sigma-Delta modulator (ΣΔM). The proposed comparator is an OR-AND-Inverter-based comparator with dual inputs and outputs, achieving a delay of 109 ps, static input offset of 591 μV, and random offset of 10.42 μV, while dissipating 890 μW, when clocked at 1.5 GHz. The proposed amplifier is a single-path three-stage inverter-based operational transcon- ductance amplifier (OTA) with active common-mode feedback loop, achieving a DC gain of 63 dB, 1444 MHz of unity-gain bandwidth, 51º of phase margin while dissipating 1098 μW, considering a load of 1 pF. The proposed comparator was employed in the ΣΔM with a standard-cell based edge- triggered flip-flop. The ΣΔM, with a sampling frequency of 2 MHz and a signal bandwidth of 2.5 kHz, achieved a peak SNDR of 69 dB while dissipating only 136.7 μW.Utilizando portas lógicas básicas em CMOS oferece a vantagem de um circuito comple- tamente sintetizável, tal como o escalamento de tensão entre tecnologias. Neste trabalho são apresentados um comparador de tensão e um amplificador utilizando portas lógicas. O objetivo deste trabalho é desenhar um comparador e um amplificador utilizando por- tas lógicas através do estudo e otimização de topologias já existentes com a finalidade de me- lhoramento de algumas das especificações das mesmas. Foram realizados vários bancos de teste para testar as topologias estudadas de compa- radores e amplificadores, em que os resultados foram comparados. As topologias de compa- radores e amplificadores de portas lógicas com melhor performance foram então modificadas. Após o comparador ter sido projetado com sucesso, foi utilizado na projeção de um modula- dor Sigma-Delta (ΣΔM) opamp-less. O comparador proposto é um OR-AND-Inversor com duas entradas e saídas, que apre- senta um atraso de 109 ps, offset estático na entrada de 591 μV, offset aleatório de 10.42 μV, enquanto dissipando 890 μW, utilizando uma frequência de relógio de 1.5 GHz O amplificador proposto é um amplificador operacional de transcondutância single- path three-stage inverter-based com um loop ativo de realimentação do modo-comum, que apresenta um ganho DC de 63 dB, 1444 MHz de ganho-unitário de largura de banda, 51º de margem de fase e dissipando 1098 μW, considerando uma carga de 1 pF. O comparador proposto foi aplicado no ΣΔM com um flip-flop edge-triggered baseado em portas lógicas. O ΣΔM, com uma frequência de amostragem de 2 MHz e uma largura de banda de 2.5 kHz, apresentou um SNDR máximo de 69 dB enquanto dissipando apenas 136.7 μW

完全自動合成可能な低電力・広入力統計的フラッシュ型A/D変換回路

This work presents a fully synthesizable stochastic flash A/D converter (SFADC), which can operate at the supply voltage of 0.6V with power consumption as low as 1.5mW at the clock frequency of 250MHz. By employing the all-digital comparator, the SFADC can be described with Verilog netlist and synthesized according to a standard digital design flow. Cross-coupled dynamic comparator structure saves the overall power due to remarkable control of dynamic power consumption. In addition, the rail-to-rail characteristic of comparator and the proposed linearity enhancement technique based on SFADC are proposed, allowing us to design a wide input-range stochastic flash ADC.北九州市立大

A Novel differential to single-ended converter for ultra-low-voltage inverter-based OTAs

For the design of inverter-based OTAs with differential input and single-ended output, the differential to single-ended (D2S) converter is a key building block. In fact, the performance of the D2S strongly affects the overall common-mode rejection ratio (CMRR) and input common-mode range (ICMR) of the whole OTA. In recent literature, inverter-based OTAs rely on a D2S topology based on an inverter driving another inverter with the input and output tight together which behaves as a “diode" connected device to implement a voltage gain approximately equal to -1. However, since this approach is based on the matching of the inverters, the performance of this D2S results sensitive to PVT variations if the bias point of the inverters is not properly stabilized. In this paper we present a novel topology of inverterbased D2S converter, exploiting an auxiliary, standard-cell-based, error amplifier and a local feedback loop. The proposed D2S, compared to the conventional one, exhibits higher CMRR, improved ICMR and better robustness with respect to PVT variations.We present also an ULV, standard-cell-based OTA, which exploits the proposed D2S converter and shows excellent performance figures of merit with low area footprint

Analog processing by digital gates: fully synthesizable IC design for IoT interfaces

Analog integrated circuits do not take advantage of scaling and are easily the bottleneck in terms of cost and performance in Internet of Things (IoT) sensor nodes integrated in nanoscale technologies. While this challenge is most commonly addressed by devising more “digital friendly” analog cells based on traditional design concepts, the possibility to translate analog functions into digital, so that to implement them by true digital gates, is now emerging as a promising alternative. This last approach, which challenges the idea that “analog circuits will be always needed”, is presented in this tutorial starting from the theoretical background to its application in digital-based operational amplifiers, voltage references, oscillators and data converters integrated on silicon which have proposed in recent literature. The applicability of the concepts to the design of ICs which are natively portable across technology nodes and highly reconfigurable, thus enabling dynamic energy quality scaling, as well as a low design effort and a fast time-to-market will be described

Re-thinking Analog Integrated Circuits in Digital Terms: A New Design Concept for the IoT Era

A steady trend towards the design of mostly-digital and digital-friendly analog circuits, suitable to integration in mainstream nanoscale CMOS by a highly automated design flow, has been observed in the last years to address the requirements of the emerging Internet of Things (IoT) applications. In this context, this tutorial brief presents an overview of concepts and design methodologies that emerged in the last decade, aimed to the implementation of analog circuits like Operational Transconductance Amplifiers, Voltage References and Data Converters by digital circuits. The current design challenges and application scenarios as well as the future perspectives and opportunities in the field of digital-based analog processing are finally discussed

A 300mV-Supply Standard-Cell-Based OTA with Digital PWM Offset Calibration

This paper introduces a fully digital pulse-width-modulation (PWM) based calibration technique intended to dynamically compensate the input offset voltage due to process and mismatch in Ultra Low Voltage (ULV) Digital-Based Operational Transconductance Amplifiers (DB-OTA). Post-layout simulations on a DB-OTA circuit in 180nm featuring the proposed calibration technique demonstrate that process and mismatch related offset voltage can be effectively compensated by varying the duty cycle of a square wave signal with minimum performance overhead. The proposed OTA consumes just 7.34nW while driving a capacitive load of 80pF with a Total Harmonic Distortion lower than 2.26% at 100mV input signal swing. The total silicon area is 1,700 um^2

Digital-Based Analog Processing in Nanoscale CMOS ICs for IoT Applications

L'abstract è presente nell'allegato / the abstract is in the attachmen

Dynamic and Static Calibration of Ultra-Low-Voltage, Digital-Based Operational Transconductance Amplifiers

The calibration of the effects of process variations and device mismatch in Ultra Low Voltage (ULV) Digital-Based Operational Transconductance Amplifiers (DB-OTAs) is addressed in this paper. For this purpose, two dynamic calibration techniques, intended to dynamically vary the effective strength of critical gates by different modulation strategies, i.e., Digital Pulse Width Modulation (DPWM) and Dyadic Digital Pulse Modulation (DDPM), are explored and compared to classic static calibration. The effectiveness of the calibration approaches as a mean to recover acceptable performance in non-functional samples is verified by Monte-Carlo (MC) post-layout simulations performed on a 300 mV power supply, nW-power DB-OTA in 180 nm CMOS. Based on the same MC post-layout simulations, the impact of each calibration strategy on silicon area, power consumption, and OTA performance is discussed