Minimum Supply Research Articles

A highly sensitive and ultra-low-power wake-up receiver for energy-autonomous embedded systems

This article presents the design, optimization and characterization of an ultra-low-power wake-up receiver for embedded wireless sensor nodes. The RF part of the circuit is based on an optimized diode detector for an amplitude-modulated (AM) 315 MHz RF carrier, followed by an ultra-low power low-frequency (LF) amplifier for the demodulated signal, and a commercial ultra-low-power wake-up receiver IC. Special emphasis has been put into optimizing the RF part with respect to its input sensitivity and selectivity. With two different versions of this circuit part, RF reception sensitivity could be raised from -52 dBm to -63 dBm. Power consumption is 7.4 µW at a minimum supply voltage of 2 V.

An Ultra-Low-Power RFID/NFC Frontend IC Using 0.18 μm CMOS Technology for Passive Tag Applications.

Battery-less passive sensor tags based on RFID or NFC technology have achieved much popularity in recent times. Passive tags are widely used for various applications like inventory control or in biotelemetry. In this paper, we present a new RFID/NFC frontend IC (integrated circuit) for 13.56 MHz passive tag applications. The design of the frontend IC is compatible with the standard ISO 15693/NFC 5. The paper discusses the analog design part in details with a brief overview of the digital interface and some of the critical measured parameters. A novel approach is adopted for the demodulator design, to demodulate the 10% ASK (amplitude shift keying) signal. The demodulator circuit consists of a comparator designed with a preset offset voltage. The comparator circuit design is discussed in detail. The power consumption of the bandgap reference circuit is used as the load for the envelope detection of the ASK modulated signal. The sub-threshold operation and low-supply-voltage are used extensively in the analog design—to keep the power consumption low. The IC was fabricated using 0.18 m CMOS technology in a die area of 1.5 mm × 1.5 mm and an effective area of 0.7 . The minimum supply voltage desired is 1.2 V, for which the total power consumption is 107 W. The analog part of the design consumes only 36 W, which is low in comparison to other contemporary passive tags ICs. Eventually, a passive tag is developed using the frontend IC, a microcontroller, a temperature and a pressure sensor. A smart NFC device is used to readout the sensor data from the tag employing an Android-based application software. The measurement results demonstrate the full passive operational capability. The IC is suitable for low-power and low-cost industrial or biomedical battery-less sensor applications. A figure-of-merit (FOM) is proposed in this paper which is taken as a reference for comparison with other related state-of-the-art researches.

The role of minimum supply and social vulnerability assessment for governing critical infrastructure failure: current gaps and future agenda

Abstract. Increased attention has lately been given to the resilience of critical infrastructure in the context of natural hazards and disasters. The major focus therein is on the sensitivity of critical infrastructure technologies and their management contingencies. However, strikingly little attention has been given to assessing and mitigating social vulnerabilities towards the failure of critical infrastructure and to the development, design and implementation of minimum supply standards in situations of major infrastructure failure. Addressing this gap and contributing to a more integrative perspective on critical infrastructure resilience is the objective of this paper. It asks which role social vulnerability assessments and minimum supply considerations can, should and do – or do not – play for the management and governance of critical infrastructure failure. In its first part, the paper provides a structured review on achievements and remaining gaps in the management of critical infrastructure and the understanding of social vulnerabilities towards disaster-related infrastructure failures. Special attention is given to the current state of minimum supply concepts with a regional focus on policies in Germany and the EU. In its second part, the paper then responds to the identified gaps by developing a heuristic model on the linkages of critical infrastructure management, social vulnerability and minimum supply. This framework helps to inform a vision of a future research agenda, which is presented in the paper's third part. Overall, the analysis suggests that the assessment of socially differentiated vulnerabilities towards critical infrastructure failure needs to be undertaken more stringently to inform the scientifically and politically difficult debate about minimum supply standards and the shared responsibilities for securing them.

Curative procedures of oral health and structural characteristics of primary dental care.

ABSTRACTOBJECTIVE To evaluate if the provision of clinical dental care, by means of the main curative procedures recommended in Primary Health Care, is associated with team structural characteristics, considering the presence of a minimum set of equipment, instrument, and supplies in Brazil’s primary health care services.METHODS A cross-sectional exploratory study based on data collected from 18,114 primary healthcare services with dental health teams in Brazil, in 2014. The outcome was created from the confirmation of five clinical procedures performed by the dentist, accounting for the presence of minimum equipment, instrument, and supplies to carry them out. Covariables were related to structural characteristics. Poisson regression with robust variance was used to obtain crude and adjusted prevalence ratios, with 95% confidence intervals.RESULTS A total of 1,190 (6.5%) dental health teams did not present the minimum equipment to provide clinical dental care and only 2,498 (14.8%) had all the instrument and supplies needed and provided the five curative procedures assessed. There was a positive association between the outcome and the composition of dental health teams, higher workload, performing analysis of health condition, and monitoring of oral health indicators. Additionally, the dental health teams that planned and programmed oral health actions with the primary care team monthly provided the procedures more frequently. Dentists with better employment status, career plans, graduation in public health or those who underwent permanent education activities provided the procedures more frequently.CONCLUSIONS A relevant number of Primary Health Care services did not have the infrastructure to provide clinical dental care. However, better results were found in dental health teams with oral health technicians, with higher workload and that plan their activities, as well as in those that employed dentists with better working relationships, who had dentists with degrees in public health and who underwent permanent education activities.

Increasing biomass demand enlarges negative forest nutrient budget areas in wood export regions

Energy production from biomass is one of the adopted strategies in different European countries to limit global warming to within the 1.5–2° targets after the 2015 UN climate agreement. This will motivate enhanced forest harvest rates and whole tree harvest to supply the increasing biomass demand. Negative nutrient budgets for certain timberland areas where geogenic nutrient supply cannot cope with harvesting rates will be one consequence. A spatially explicit analysis for a U.S. timberland area of 33,570 km2 reveals that for a minimum nutrient loss and supply scenario, negative nutrient budgets occur in 17, 20, 16, and almost 94% of the studied areas for Ca, K, Mg, and P, respectively. For a maximum nutrient loss (considering intensive harvesting) and supply assumptions, the affected areas increase to 50, 57, 45 and 96% for Ca, K, Mg, and P, respectively. In general, atmospheric nutrient deposition is of minor importance for the high weathering supply cases. Increasing global woody biomass demand may cause additional pressure on forested ecosystems, enlarging negative nutrient budget areas. If woody biomass demand rises, strategies to counterbalance nutrient gaps might be needed, for example, by preparing harvested areas with rock products, designed to replenish growth limiting nutrients, and/or implementing forest management strategies to minimize nutrient export.

A 220 mV robust read-decoupled partial feedback cutting based low-leakage 9T SRAM for Internet of Things (IoT) applications

In this work, a 9T subthreshold SRAM cell is proposed with the reduced leakage power and improved stability against the PVT variations. The proposed cell employs the read decoupling to improve the read stability, and the partial feedback cutting approach to control the leakage power with improved read/write ability. The incorporated stacking effect further improves the leakage power. The simulated leakage power for the proposed cell is 0.61×, 0.49×, 0.80× and 0.55×, while the read static noise margin (RSNM) is 2.5×, 1×, 1.05× and 0.96×, write static noise margin (WSNM) 0 is 1.5×, 1.8×, 1.68× and 1.9× and WSNM 1 is 0.95×, 1.2×, 1.05×, and 1.2× at 0.4 V when compared with the conventional 6T and state of arts (single ended 6T, PPN based 10T and data aware write assist (DAWA) 12T SRAM architectures) respectively. The minimum supply voltage at which this cell can successfully operate is 220 mV. A 4 Kb memory array has also been simulated using proposed cell and it consumes 0.63×, 0.67× and 0.63× less energy than 6T during read, write 1 and write 0 operations respectively for supply voltage of 0.3 V.

Reliable high-yield CNTFET-based 9T SRAM operating near threshold voltage region

We propose a reliable high-yield nine-carbon-nanotube field-effect transistor (9-CNTFET) static random-access memory (SRAM) cell using shared bit line and half-select-free techniques. The proposed SRAM cell operates near the threshold voltage of 325 mV. The proposed cell was also tested and verified under process variation, exhibiting stable write and read operations. Due to the reduced leakage current of the proposed cell, the power consumption is significantly decreased by 4.98-fold compared with the conventional six-transistor (6T) cell. Although the use of a CNT array increases the probability of functionality of the CNTFET, it occupies 1 % more area. Due to its high $$I_{\mathrm{ON}}/I_{\mathrm{OFF}}$$ ratio, shortest node, shared bit line, and high-efficiency read and write ports, the read and write access time of the proposed nine-transistor (9T) SRAM cell is improved by 43 and 98 %, respectively, compared with the conventional 6T device. When using the low-feature-size CNTFET device in a new 9T SRAM cell, the area overhead is reduced to 32.9 % compared with previously published 9T SRAM cells. The proposed cell operates with minimum supply voltage near the threshold voltage region, reducing the read and write power consumption per bit by 1.2- and 1.8-fold, respectively, compared with existing 9T SRAM cells.

Acute Limb Ischemia-Much More Than Just a Lack of Oxygen.

Acute ischemia of an extremity occurs in several stages, a lack of oxygen being the primary contributor of the event. Although underlying patho-mechanisms are similar, it is important to determine whether it is an acute or chronic event. Healthy tissue does not contain enlarged collaterals, which are formed in chronically malperfused tissue and can maintain a minimum supply despite occlusion. The underlying processes for enhanced collateral blood flow are sprouting vessels from pre-existing vessels (via angiogenesis) and a lumen extension of arterioles (via arteriogenesis). While disturbed flow patterns with associated local low shear stress upregulate angiogenesis promoting genes, elevated shear stress may trigger arteriogenesis due to increased blood volume. In case of an acute ischemia, especially during the reperfusion phase, fluid transfer occurs into the tissue while the vascular bed is simultaneously reduced and no longer reacts to vaso-relaxing factors such as nitric oxide. This process results in an exacerbative cycle, in which increased peripheral resistance leads to an additional lack of oxygen. This whole process is accompanied by an inundation of inflammatory cells, which amplify the inflammatory response by cytokine release. However, an extremity is an individual-specific composition of different tissues, so these processes may vary dramatically between patients. The image is more uniform when broken down to the single cell stage. Because each cell is dependent on energy produced from aerobic respiration, an event of acute hypoxia can be a life-threatening situation. Aerobic processes responsible for yielding adenosine triphosphate (ATP), such as the electron transport chain and oxidative phosphorylation in the mitochondria, suffer first, thus disrupting the integrity of cellular respiration. One consequence of this is irreparable damage of the cell membrane due to an imbalance of electrolytes. The eventual increase in net fluid influx associated with a decrease in intracellular pH is considered an end-stage event. Due to the lack of ATP, individual cell organelles can no longer sustain their activity, thus initiating the cascade pathways of apoptosis via the release of cytokines such as the BCL2 associated X protein (BAX). As ischemia may lead to direct necrosis, inflammatory processes are further aggravated. In the case of reperfusion, the flow of nascent oxygen will cause additional damage to the cell, further initiating apoptosis in additional surrounding cells. In particular, free oxygen radicals are formed, causing severe damage to cell membranes and desoxyribonucleic acid (DNA). However, the increased tissue stress caused by this process may be transient, as radical scavengers may attenuate the damage. Taking the above into final consideration, it is clearly elucidated that acute ischemia and subsequent reperfusion is a process that leads to acute tissue damage combined with end-organ loss of function, a condition that is difficult to counteract.

Design Considerations for a Sub-mW Wireless Medical Body-Area Network Receiver Front End

Wireless medical body-area networks are used to connect sensor nodes that monitor vital parameters. The radio consumes a large portion of the sensor energy budget, and hence its power dissipation should be minimized. The low-noise amplifier (LNA) is an important component of the receiver, and must guarantee low-noise amplification and impedance matching. In this work, an ultra-low-voltage ultra-low-power LNA is proposed that, thanks to the proposed transformer-based gate boosting technique, has a reduced current consumption of only 160 μA and can operate with a supply as low as 0.18 V. The LNA was designed using 40 nm Complementary Metal-Oxide Semiconductor (CMOS) technology and features a voltage gain of 14 dB, 5.2 dB NF and −8.6 dBm IIP3. This performance is comparable to a prior work by the same authors, but with the minimum supply voltage reduced by a factor of 4x.

Multi-objective Optimization of Transmission Line Annual Maintenance Scheduling Based on Flower Pollination Algorithm

The optimization of the annual maintenance scheduling is a multidimensional and nonlinear integer optimization problem. In this paper, the annual maintenance scheduling model is established with the minimum cost of maintenance and the expected minimum power supply, and the pollination algorithm based on e constraint is proposed. By obtaining the Pareto optimal solutions and comparing the economic and reliability objectives of the optimization problem of the maintenance scheduling, the proposed algorithm can effectively improve the solution precision of the multi - objective optimization problem and the distribution of the optimal solution. Based on the annual inspection scheduling of 12 transmission lines in a region, this paper compares the proposed algorithm with the Differential Evolution Flower Pollination Algorithm with Time Variant Factor (TVDFPA) and the Simulated Annealing Pollination Algorithm (SFPA). Based on the result, e-constrained algorithm is superior to the other two in performance and calculation time.

High-temperature electrolysis of CO2–enriched mixtures by using fuel-electrode supported La0.6Sr0.4CoO3/YSZ/Ni-YSZ solid oxide cells

To mitigate CO2 emissions, its reduction by high-temperature electrolysis using solid oxide cells is extensively investigated, for which excessive steam supply is assumed. However, such condition may degrade its feasibility due to massive energy required for generating hot steam, implying the needs for lowering steam demand. In this study, high-temperature electrolysis of CO2-enriched mixtures by using fuel-electrode supported La0.6Sr0.4CoO3/YSZ/Ni-YSZ solid oxide cells is considered to satisfy such needs. The effect of internal and external steam supply on its electrochemical performance and gas productivity is elucidated. It is shown that the steam produced in-situ inside the fuel-electrode by a reverse water gas shift reaction may decrease significantly the electrochemical resistance of dry CO2-fed operations, attributed to self-sustaining positive thermo-electrochemical reaction loop. This mechanism is conspicuous at low current density, whereas it is no longer effective at high current density in which total reactant concentrations for electrolysis is critical. To overcome such limitations, a small amount of external steam supply to the CO2-enriched feed stream may be needed, but this lowers the CO2 conversion and CO/H2 selectivity. Based on these results, it is discussed that there can be minimum steam supply sufficient for guaranteeing both low electrochemical resistance and high gas productivity.

A 1.2 V, 3.0 ppm/°C, 3.6 μA CMOS bandgap reference with novel 3-order curvature compensation

This paper presents a bandgap reference with a high-order curvature compensation circuit which can improve the temperature coefficient (TC) in a wide temperature range. The proposed compensation circuit includes a second-order and a third-order curvature current generators as well as an I-V converter. These two curvature currents are achieved by utilizing the exponential behavior of sub-threshold MOSFET and used for compensating the high-order temperature dependence of BJT base-emitter voltage via I-V converter. The proposed BGR is implemented in a CMOS 0.18 μm process with the active area of 0.056 mm2. Measurements on ten samples showed that at the minimum supply voltage 1.2 V, the TC varies from 1.7 to 6.9 ppm/°C over a temperature range of 170 °C (−45 °C–125 °C) with an average value of 3.0 ppm/°C and the total current consumption of 3.6 μA at room temperature. In the supply voltage range of 1.2–1.8 V, the line regulation (LR) is 0.025%/V.

Direct Current Charger Hardware Platform Design

In order to reduce the pollution caused by fuel vehicles to the environment, electric vehicles are becoming the means of transportation. The replacement of fuel vehicles by electric vehicles is a future trend. Based on practical requirements, a 120 kW direct current charger has been designed. Taking the MK60DN512 as the core controller, a direct current charger control system is designed and implemented. The overall solution of the direct current charger control system is designed. According to the functional requirements of the direct current charger, a system hardware platform is built based on embedded technology. The hardware mainly consists of MK60DN512 microcontroller, start/reset circuit, JTAG download/debugging circuit, clock circuit, minimum system power supply, output voltage sampling and signal conversion circuit, output current sampling and signal conversion circuit, AC relay control circuit and temperature detection circuit.

Study on water resources optimal regulation of inter-basin water transfer project

Water resources optimal regulation is an important means to mitigate the shortage of water resources and promote social and economic sustainable development in regions or watershed. With the rapid development of urban population and industrial and agricultural production in recent years, the shortage of water is becoming more and more serious in Jiaodong area. The four regions with serious water shortage including Weifang, Qingdao, Yantai and Weihai in Jiaodong area are the typical research areas. In combination with the water transfer project of Yellow river to Qingdao and the south-to-north water transfer project, the water diversion is carried out to alleviate the contradiction between water supply and demand of Jiaodong area. The year of 2014 deemed as the base year and the years of 2020 and 2025 are the planning years. Based on the supply and demand analysis of water resources, an optimal regulation model is built with the minimum total water shortage considering the constraints of water supply capacity of project, water distribution capacity and minimum water supply of bleeds and so on. The optimal regulation schemes are obtained by solution model using MATLAB programming. The results show that water shortage rate of the four cities decreases significantly in annual regulation. For different planning years, guarantee rate of 50%, 75% and 95%,the total water shortage rate will be reduced by 15.35%、15.75% and 16.85% respectively in 2020, and in 2025the total water shortage rate will be reduced by 13.27%、13.26% and 14.19% respectively. Therefore the water resources optimal regulation of inter-basin water transfer project can effectively mitigate water scarcity and the contradiction between water supply and demand in Jiaodong area.

A Nano-Watt MOS-Only Voltage Reference With High-Slope PTAT Voltage Generators

This brief presents an MOS-only voltage reference circuit with high-slope proportional-to-absolute-temperature (PTAT) voltage generators for ultra-low-power applications. Biased by a nano-ampere current reference circuit, the PTAT voltage generator is realized by an asymmetrical differential cell with two additional cross-coupled nMOS/pMOS pairs, which enhance the slope of the PTAT voltage remarkably. As a result, only two cascaded PTAT stages are used to compensate the complementary-to-absolute-temperature voltage generated directly by a diode-connected nMOS in the current reference circuit. Therefore, much power and chip area can be saved. A trimming circuit is also adopted to compensate the process-related reference voltage variations. The experimental results of the proposed reference circuit fabricated in a 0.18- $ {\mu }$ m standard CMOS process demonstrate that the circuit could operate under a minimum supply voltage of 1 V, and generate a reference voltage of 756 mV with temperature coefficient of 74 and 49.6 ppm/°C under 1-V and 1.8-V power supply, respectively. The proposed circuit consumes only 23 nA under a 1-V power supply, and the active area is only 95 $ {\mu }\text{m}\,\, {\times } \,\, 170 ~{\mu }\text{m}$ .

0.23-V Sample-Boost-Latch-Based Offset Tolerant Sense Amplifier

An offset tolerant SRAM sense amplifier (SA) deployed with sample-boost-latch technique to facilitate both common mode and differential mode boosting is proposed. The common mode boosting enables proposed SA, SBLSA to operate deeper into the subthreshold regime whereas the differential mode boosting helps tolerate undesirable mismatch conditions by driving cross-coupled inverters with boosted differential voltages. The proposed boosting circuit first samples the bitline voltages and then isolates the sampled voltages from the highly capacitive bitlines followed by the boosting phase on relatively much less internal input capacitances of the latch. Arrays of SBLSA and conventional voltage latch SA (VLSA) were fabricated in 65-nm-GP CMOS (512 each). At 25 °C, SBLSA achieves 23.3% reduction in directly measured standard deviation of input-referred offset (across 16 ICs, 8192 SAs) and 38.5% improvement (typical IC) in sensing delay at 0.3 V. SBLSA offers reliable operation across entire temperature range of −25 °C to 85 °C at 0.35 V whereas it is 0.41 V for VLSA. Finally, SBLSA operates reliably at the minimum supply of 0.23 V at 25 °C which is 30 mV less compared to VLSA.

Picowatt, 0.45–0.6 V Self-Biased Subthreshold CMOS Voltage Reference

In this paper, a self-biased temperature-compensated CMOS voltage reference operating at picowatt-level power consumption is presented. The core of the proposed circuit is the self-cascode MOSFET (SCM) and two variants are explored: a self-biased SCM (SBSCM) and a self-biased NMOS (SBNMOS) voltage reference. Power consumption and silicon area are remarkably reduced by combining subthreshold operation with a self-biased scheme. Trimming techniques for both circuits are discussed aiming at the reduction of the process variations impact. The proposed circuits were fabricated in a standard 0.18- $\mu \text{m}$ CMOS process. Measurement results from 24 samples of the same batch show that both circuits herein proposed can operate at 0.45/0.6 V minimum supply voltage, consuming merely 55/184 pW at room temperature. Temperature coefficient (TC) around 104/495 ppm/°C across a temperature range from 0 to 120 °C was measured. Employment of a trimming scheme allows a reduction of the average TC to 72.4/11.6 ppm/°C for the same temperature range. Both variants of the proposed circuit achieve a line sensitivity of 0.15/0.11 %/V and a power supply rejection better than −44/−45 dB from 10 to 10 kHz. In addition, SBSCM and SBNMOS prototypes occupy a silicon area of 0.002 and 0.0017 mm2, respectively.

Modeling of positive pressure ventilation to prevent smoke spreading in sprinklered high-rise buildings

This paper analyzes the positive pressure ventilation to prevent the smoke from entering the stairwell using Large Eddy Simulation in a sprinklered high-rise building with the heat release rate of 1.5 MW. Two methods are compared to get a more effective way: (1) the pressurization air flow into the stairwell from the group of multiple air supply outlets, and (2) the group of 2 air supply outlets next to the fire floor. The results have shown that to prevent the smoke from entering the stairwell, the minimum pressurization air supply volume flow rates are less in the group of 2 air supply outlets than those in the group of multiple air supply outlets. When the pressurization fan is located on the top of the stairwell, based on the mass and energy conservation, a simple method is developed to predict the airflow mass flow rates at the outlets. Further, the correlation of the average pressure in the stairwell on the fire floor and the pressurization air supply volume flow rate is developed. The minimum pressurization air supply volume flow rate to obtain smoke free zone and maximum one to avoid the door being too heavy to open during evacuation can be estimated.

A Low-Power CMOS Crystal Oscillator Using a Stacked-Amplifier Architecture

This paper presents a low-power 39.25-MHz crystal oscillator with a new stacked-amplifier architecture achieving the smallest figure of merit (FoM) ever reported for a crystal oscillator for wireless communications. Theoretical analyses of the power consumption and the phase noise (PN) in the proposed stacked-amplifier architecture are newly provided to clarify the reason why the proposed stacked-amplifier architecture achieves the smallest FoM. Additionally, a new self-forward-body-biasing technique and flicker noise suppression technique are shown to reduce the minimum operational supply voltage (VDD(MIN)) and the PN, respectively. The proposed 3.3-V, 39.25-MHz stacked-amplifier crystal oscillator fabricated in a 65-nm CMOS process exhibits the smallest FoM for a crystal oscillator of −248 dBc/Hz with a power consumption of 19 $\mu \text{W}$ and PN of −139 dBc/Hz at 1-kHz offset frequency. The relative frequency errors among 11 samples at temperatures of −30 °C to 80 °C and for ±10% supply voltage variation are ±10.5 ppm and ±0.12 ppm, respectively. The long-term frequency error is −0.98 ppm in the first year (=365 days).

Ultra-Sub-Threshold Operation of Always-On Digital Circuits for IoT Applications by Use of Schmitt Trigger Gates

Supply-voltage reduction in digital circuits beyond the minimum energy per operation point is advantageous for supply-voltage-constrained applications and can help to considerably reduce standby power consumption. Schmitt trigger (ST) logic allows for ultra-low voltage (ULV) operation; hardware implementations with supply voltages as low as 62mV have been demonstrated. In this paper, a systematic in-depth analysis of ST logic is presented. First, it is shown that ST logic allows for operation at supply voltages below the ultimate limit of standard digital CMOS circuits, making it—to the best of our knowledge—the only approach proposed to date for operation of digital circuits in this voltage region. The factors critical to the ultimate limit of supply voltage reduction are the ON-to-OFF current ratio of the transistors and the susceptibility to global variability. It is shown that ST logic provides improvements over standard CMOS logic in both of these aspects. The hysteresis that occurs in ST circuits at nominal supply voltage could potentially limit the applicability for ULV operation and is therefore carefully investigated. Furthermore, a systematic approach to optimum sizing of ST gates is presented for the first time. ST gates exhibit inherent overheads with respect to gate area, delay, and leakage, which are carefully evaluated. Compared with standard CMOS gates designed for the same minimum supply voltage, it is shown that ST gates, nevertheless, are the most efficient solution if the target minimum supply voltage is sufficiently low: with respect to area, this limit is at $V_{DD}\approx 110\,mV$ and with respect to power/delay at $V_{DD}\approx 75\,mV$ .