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In this paper, we describe a design of a mixed-signal circuit for an binary neuron (a.k.a perceptron, threshold logic gate) and a methodology for automatically embedding such cells in ASICs. The binary neuron, referred to as an FTL (flash threshold logic) uses floating gate or flash transistors whose threshold voltages serve as a proxy for the weights of the neuron. Algorithms for mapping the weights to the flash transistor threshold voltages are presented. The threshold voltages are determined to maximize both the robustness of the cell and its speed. The performance, power, and area of a single FTL cell are shown to be significantly smaller (79.4%), consume less power (61.6%), and operate faster (40.3%) compared to conventional CMOS logic equivalents. Also included are the architecture and the algorithms to program the flash devices of an FTL. The FTL cells are implemented as standard cells, and are designed to allow commercial synthesis and P&R tools to automatically use them in synthesis of ASICs. Substantial reductions in area and power without sacrificing performance are demonstrated on several ASIC benchmarks by the automatic embedding of FTL cells. The paper also demonstrates how FTL cells can be used for fixing timing errors after fabrication [ABSTRACT FROM AUTHOR]

The performance of nanoscale semiconductor technologies has become susceptible to high temperatures and aging phenomena. While guard-bands have conventionally been used to combat degradation-induced timing violations, approximations have recently been leveraged to compensate for degradations in lieu of adding timing guard-bands, without a loss in performance. However, only simple approximation techniques such as truncation have been considered in prior work. In this paper, a wide range of approximate arithmetic circuits including adders and multipliers using various sophisticated approximation techniques are investigated to cope with aging- and temperature-induced degradations. To this end, approximate circuits are first characterized for their delay increase under degradations. With this, we then determine the approximation level required to compensate for guard-bands under different degradations. Degradation-aware logic synthesis results show that the simple use of truncated arithmetic circuits leads to a higher quality loss compared to using other approximate circuits. However, a truncated multiplier has the lowest error distance towards a reliable operation in 10 years. The approximate multipliers with configurable error recovery are most suitable when the level of degradation is higher, e.g., at a temperature of 70 °C. The characterization of degradation at the circuit level is then used for design exploration at the architecture level without the need for further gate-level simulations. For three different image processing applications, experimental results show that guard-bands can be mitigated while maintaining an output result with a high visual quality. [ABSTRACT FROM AUTHOR]

This paper presents a tunable new deadtime control circuit providing an optimal delay for power converter optimization. Our method can reduce the deadtime loss while improving the efficiency and power density of a given power converter. The circuit presents a reconfigurable delay element to generate a wide range of deadtime for different power conversion applications with varying loads and input voltages. The optimal deadtime equation for buck converters is derived, and its dependency on the input voltage and load is discussed. Experimental results show that the presented circuit can provide a wide range of deadtime delays, ranging from 9.2 ns to 1000 ns. The power consumption of the presented circuit is measured for different capacitive loads ($\text{C}_{\mathrm {L}}$) and operating frequencies (${f}_{\mathrm {s}}$). The circuit consumed a power between 610 $\mu \text{W}$ and $850~\mu \text{W}$ across the measured deadtime ranges while $\text{C}_{\mathrm {L}} =12$ pF, $\text{V}_{\mathrm {dd}} =3.3$ V, and $\text{f}_{\mathrm {s}}=200$ kHz. The proposed deadtime generator can operate up to 18 MHz when the minimum deadtime of 9.2 ns is selected. The presented circuit occupies an area of $150\mu $ m $\times 260\mu \text{m}$. The fabricated chip is connected to a buck converter to validate the operation of the proposed circuit. The efficiency of a typical buck converter with minimum $\text{T}_{\mathrm {DLH}}$ and optimal $\text{T}_{\mathrm {DHL}}$ at $\text{I}_{\mathrm {Load}} =25$ mA is improved by 12% compared to a converter with a fixed deadtime of $\text{T}_{\mathrm {DLH}} =\,\,\text{T}_{\mathrm {DHL}} =12$ ns. [ABSTRACT FROM AUTHOR]

With the advancement of technology, the size of transistors and the distance between them are reducing rapidly. Therefore, the critical charge of sensitive nodes is reducing, making SRAM cells, used for aerospace applications, more vulnerable to soft-error. If a radiation particle strikes a sensitive node of the standard 6T SRAM cell, the stored data in the cell are flipped, causing a single-event upset (SEU). Therefore, in this paper, a Soft-Error-Aware Read-Stability-Enhanced Low-Power 12T (SARP12T) SRAM cell is proposed to mitigate SEUs. To analyze the relative performance of SARP12T, it is compared with other recently published soft-error-aware SRAM cells, QUCCE12T, QUATRO12T, RHD12T, RHPD12T and RSP14T. All the sensitive nodes of SARP12T can regain their data even if the node values are flipped due to a radiation strike. Furthermore, SARP12T can recover from the effect of single-event multi-node upsets (SEMNUs) induced at its storage node-pair. Along with these advantages, the proposed cell exhibits the highest read stability, as the ‘0’-storing storage node, which is directly accessed by the bitline during read operation, can recover from any upset. Furthermore, SARP12T consumes the least hold power. SARP12T also exhibits higher write ability and shorter write delay than most of the comparison cells. All these improvements in the proposed cell are obtained by exhibiting only a slightly longer read delay and consuming slightly higher read and write energy. [ABSTRACT FROM AUTHOR]

This paper explores a low standby power 10T (LP10T) SRAM cell with high read stability and write-ability (RSNM/WSNM/WM). The proposed LP10T SRAM cell uses a strong cross-coupled structure consisting standard inverter with a stacked transistor and Schmitt-trigger inverter with a double-length pull-up transistor. This along with the read path separated from true internal storage nodes eliminates the read-disturbance. Furthermore, it performs its write operation in pseudo differential form through write bitline and control signal with a write-assist technique. To estimate the proposed LP10T SRAM cell’s performance, it is compared with some state-of-the-art SRAM cells using HSPICE in 16-nm CMOS predictive technology model at 0.7 V supply voltage under harsh manufacturing process, voltage, and temperature variations. The proposed SRAM cell offers 4.65X/1.57X/1.46X improvement in RSNM/WSNM/WM and 4.40X/1.69X narrower spread in RSNM/WM compared to the conventional 6T SRAM cell. Furthermore, it shows 1.26X/1.08X/1.01X higher RSNM/WSNM/WM and 1.71X/1.25X tighter/wider spread in RSNM/WM compared to the best studied SRAM cells. The proposed SRAM cell indicates 74.48%/1.41% higher/lower read/write delay compared to the 6T SRAM cell. Moreover, it exhibits the third-(second-) best read (write) dynamic power, consuming 29.69% (26.87%) lower than the 6T SRAM cell. The leakage power is minimized by the proposed design, which is 37.35% and 12.08% lower than that of the 6T and best studied cells, respectively. Nonetheless, the proposed LP10T SRAM cell occupies 1.313X higher area compared to the 6T SRAM cell. [ABSTRACT FROM AUTHOR]

This paper investigates the metastability of true single-phase clock (TSPC) D flip flops (DFFs) and its impact on the resolution of Vernier time-to-digital converters (TDCs). The mechanisms of the metastability of TSPC DFFs are investigated and the analytical expressions of setup time and hold time are obtained. A shunt capacitor technique capable of reducing setup time and hold time to zero with no power and delay penalty is proposed. The impact of PVT (process, voltage, temperature) on the effectiveness of the proposed technique is quantified using simulation. Vernier TDCs, both right-shifting and left-shifting, with untuned and tuned DFFs are designed in TSMC 130 nm 1.2 V CMOS technology and analyzed using Spectre with BSIM3V3 device models. Simulation results demonstrate TDCs with tuned DFFs enjoy zero conversion error while the right-shifting and left-shifting TDCs with untuned DFFs have 1-bit and 5-bit conversion errors or 11% and 56% error rates, respectively. [ABSTRACT FROM AUTHOR]

One of the major barriers that CMOS devices face at nanometer scale is increasing parameter variation due to manufacturing imperfections. Process variations severely inhibit the reliable operation of circuits, as the operational frequency at the nominal process corner is insufficient to suppress timing violations across the entire variability spectrum. To avoid variability-induced timing errors, previous efforts impose pessimistic and performance-degrading timing guardbands atop the operating frequency. In this work, we employ approximate computing principles and propose a circuit-agnostic automated framework for generating variability-aware approximate circuits that eliminate process-induced timing guardbands. Variability effects are accurately portrayed with the creation of variation-aware standard cell libraries, fully compatible with standard EDA tools. The underlying transistors are fully calibrated against industrial measurements from Intel 14nm FinFET in which both electrical characteristics of transistors and variability effects are accurately captured. In this work, we explore the design space of approximate variability-aware designs to automatically generate circuits of reduced variability and increased performance without the need for timing guardbands. Experimental results show that by introducing negligible functional error of merely $\boldsymbol {5.3 \times 10^{-3}}$ , our variability-aware approximate circuits can be reliably operated under process variations without sacrificing the application performance. [ABSTRACT FROM AUTHOR]

Transistor aging phenomena manifest themselves as degradations in the main electrical characteristics of transistors. Over time, they result in a significant increase of cell propagation delay, leading to errors due to timing violations, since the operating frequency becomes unsustainable as the circuit ages. Conventional techniques employ timing guardbands to mitigate aging-induced delay increase, which leads to considerable performance losses from the beginning of the circuit’s lifetime. Leveraging the inherent error resilience of a vast number of application domains, approximate computing was recently introduced as an aging mitigation mechanism. In this work, we present the first automated framework for generating aging-aware approximate circuits. Our framework, by applying directed gate-level netlist approximation, induces a small functional error and recovers the delay degradation due to aging. As a result, our optimized circuits eliminate aging-induced timing errors. Experimental evaluation over a variety of arithmetic circuits and image processing benchmarks demonstrates that for an average error of merely $5\times 10^{-3}$ , our framework completely eliminates aging-induced timing guardbands. Compared to the respective baseline circuits without timing guardbands (i.e., iso-performance evaluation), the error of the circuits generated by our framework is $1208\times $ smaller. [ABSTRACT FROM AUTHOR]

With aggressive scaling of transistor size and supply voltage, the critical charge of the sensitive nodes is reducing rapidly. As a result, when these deep submicron devices are used in memory cells in the space environment, single-event upsets (SEUs), also known as soft-errors, pose a great threat to the reliability of the cells. To mitigate the effects of SEUs, we propose a soft-error-immune read-stability-improved (SIRI) SRAM cell. To assess the performance of the proposed cell, it is compared with other soft-error-immune SRAM cells, namely, QUCCE12T, WE-QUATRO, RHPD12T, RHBD14T and RSP14T. Simulation results confirm that the detrimental effects of SEUs do not alter the state of SIRI as all the sensitive nodes can reattain their initial states after being impacted by an SEU. The cell can also recover from single-event multi-node upsets (SEMNUs) that occur at its storage node-pair. Moreover, the storage nodes of the proposed cell are isolated from the bitlines during read operation. Hence, it exhibits the highest read stability. The write ability and write delay of SIRI are also superior to those of the majority of the comparison cells, and it consumes much lower hold power than many of the conventional SRAM cells. All these improvements are brought about only at the expense of a slightly longer read delay. [ABSTRACT FROM AUTHOR]