Abstract

This paper proposes low power optimization using a modified swarm intelligence algorithm for the scenariostransistor sizing based static power reduction and low power standard cell generation for approximate computing. In these scenarios, we explore a lower abstraction level and see how standard cells can be tuned to a power-delay-quality optimal point. For transistor sizing, the algorithm considers fabrication process parameter variations (for ±3σ design) in addition to a wide range of temperature (-55oC to 125oC) and supply voltage (±10%) variations to yield PVT aware robust sizing solutions. The approach has been applied on numerous single and multistage circuits (including ISCAS benchmarks) while proposing a dual sizing solution for non-critical and critical path cells. For approximate systems, we present algorithm-generated full adder designs for speech processing systems. The designs vary in terms of accuracy and power. Results show leakage reductions up to 58.2% for conventional and 66.8% with approximation designs for 22nm metal gate high-K (MGK) technology cells.

Abstract

In this paper, we aim at optimizing the leakage power and propagation delays using optimization algorithms like Glowworm Swarm Optimization and Neighbourhood Cultivation Genetic Algorithm, subjected to variations in Process, Voltage, Temperature and Aging degradation (PVTA) targeting low power or high performance applications. For high performance ap­plications, we synthesize transistor sizes, at which the critical path delay in worst case PVT conditions with 3 years of NBTI aging degradation is optimized below the critical path delay (of initial sizing) at nominal conditions keeping power budget in bound. On the other hand, for low power applications, we obtain transistor sizing where leakage is reduced by more than 50%, keeping a bound on critical path delay. All the pre and post stress simulations are performed using HSPICE for 22nm Metal Gate High-K dielectric model parameters. The temperature range and the supply voltage ranges are −55 °C to 125 °C and 0.72V to 0.88V respectively. The process parameters are considered at ±3σ variation. The ingenuous working of the circuits for the obtained sizing is ensured by Monte Carlo analysis evaluating over entire range of process variations and operating conditions for intended life time.

Abstract

The paper presents a sub-nW BJT based temperature sensor for ultra-low power microsystems. The sensor is based on amplifying the difference between baseemitter voltages of BJTs using gate-leakage transistors. Implemented in UMC 65nm technology, the sensor occupies an area of 0.005mm2 . It achieves a maximum non-linearity error of 0.12oC(3σ) over the temperature range of −55oC to 80oC. Without any trimming, a worst case inaccuracy of +0.36oC/ − 1.61oC is observed w.r.t process variations, depicting the process-invariant nature of the temperature sensor. It also achieves a low supply sensitivity of 0.56oC/V over a wide supply range of 0.7V-3V. The power consumption of the sensor is 419pW at 27oC and 0.7V supply.

Abstract

[0002] Resistors are the essential and common elements of any electronic circuits and extensively used in electronic equipment. They are frequently used in Integrated Circuits. The conventional on-chip resistance takes a large silicon area compared to metal oxide 15 semiconductor MOS transistor. In fabrication, the area is proportional to cost. If the silicon area is more, then the cost of the chip also increases. Therefore, large resistances are avoided to fabricate on the chip. For low power circuits, large resistances are often required but due to limited silicon area they are avoided. Hence the conventional resistor is replaced by a complementary metal-oxide-semiconductor CMOS circuit or a switched capacitor-based 20 resistor circuit to save area.

Abstract

This work presents a highly accurate current reference of 66nA for ultra-low power applications. A very low figureof-merit (FOM) of 1.3501ppm/◦C 2 is achieved on consuming a minimal quiescent current of 199.37nA. To cancel out process variations, the current subtraction technique is employed and a β-multiplier is used to compensate for mobility (µ) and threshold voltage (Vth). In addition, curvature compensation technique backed by PTAT and CTAT current cancellation is adopted to attain a lower temperature coefficient (TC). Hence, an imperceptible variation of accuracy with temperature and supply variations across all process corners is attained. An adopted trimming scheme further minimizes the overall process spread to ±1.515% without compromising on accuracy. Accordingly, a TC of 67.04ppm/◦C over a wide temperature range of -50◦C to 100◦C is obtained. Furthermore, 1.413%/V line sensitivity (LS) in the supply range of 1.38V to 3V is observed. Low power consumption of 275.13nW@1.38V facilitates its use in high-performance low power applications. Index Terms—FOM, curvature compensation, Line Sensitivity, Proportional to Absolute Temperature (PTAT), Complementary to Absolute Temperature (CTAT), ZTC

Abstract

This brief presents a CMOS-only ultra low power voltage reference of 0.925V which is designed and simulated in TSMC 180nm technology. Current mixing between SelfBiased Self Cascode MOSFET (SBSCM) and Self Cascode MOSFET (SCM) pair is introduced along with stacking of proportional to absolute temperature (PTAT) and complementary to absolute temperature (CTAT) voltage generators to get second order curvature compensation. Temperature coefficient (TC) of 3.75ppm/◦C over a wide temperature range of -55◦C to 140◦C is achieved. To feed on the power reduction requirement of low power biomedical applications, the entire circuit is designed in sub-threshold region. Therefore, the total power consumption is 27nW @ 1.45V at room temperature (27◦C). Furthermore, a supply independent current bias aids in realizing high PSRR of -91dB @ 10Hz / -50dB @ 100MHz and line regulation of 0.0779%/V over a supply range 1.45V to 3.6V. Besides, an employed trimming technique attenuates the process spread from ±3% to ±0.3%. Moreover, the proposed design occupies an active area of 0.0054mm2 only. Index Terms—Ultra Low Power, Voltage Reference, PSRR, CTAT, PTAT, Biomedical, SBSCM, SCM.

Abstract

This brief presents a CMOS-only ultra low power voltage reference of 0.925V which is designed and simulated in TSMC 180nm technology. Current mixing between SelfBiased Self Cascode MOSFET (SBSCM) and Self Cascode MOSFET (SCM) pair is introduced along with stacking of proportional to absolute temperature (PTAT) and complementary to absolute temperature (CTAT) voltage generators to get second order curvature compensation. Temperature coefficient (TC) of 3.75ppm/°C over a wide temperature range of -55°C to 140°C is achieved. To feed on the power reduction requirement of low power biomedical applications, the entire circuit is designed in sub-threshold region. Therefore, the total power consumption is 27nW @ 1.45V at room temperature (27°C). Furthermore, a supply independent current bias aids in realizing high PSRR of -91dB @ 10Hz / -50dB @ 100MHz and line regulation of 0.0779%/V over a supply range 1.45V to 3.6V. Besides, an employed trimming technique attenuates the process spread from ±3% to ±0.3%. Moreover, the proposed design occupies an active area of 0.0054mm 2 only.

Abstract

This brief presents a novel PVT-invariant CMOS relaxation oscillator for Real-Time Clock (RTC) applications. The proposed design is compatible to work in a low supply voltage domain of SoC. The PVT invariance is achieved by a unique circuit implementation of introducing a self-adaptive mechanism that dynamically modifies the time constant of the oscillator core. Moreover, the design is accompanied by a digital calibration unit for further process compensation. Besides, the introduced supply independent bias circuit has greatly improved the supply regulation of the oscillator frequency. In addition, the design utilizes a complementary to absolute temperature (CTAT) current for temperature compensation. Area efficiency is enhanced by replacing bigger passive device i.e, resistor with an adaptive MOS resistor. The obtained results show that the minimum temperature coefficient (TC) of 31.236ppm/°C is achieved over a range of -40°C to 100°C. The resultant phase noise of -140dBc/Hz@1MHz is observed. The design has achieved a good power efficiency of 1.65nW/KHz at room temperature without a calibration unit. The line sensitivity (LS) of 0.1159%/V is noted in the range of 0.7V to 1.2V. Nevertheless, the entire system occupies an active area of 0.0509mm^2 with a power consumption of 90nW@0.7V. Also, the leakage current of the complete system is <; 54pA. Therefore, the proposed design aims at providing a production-friendly, ease of integration and low-cost solution.

Abstract

he paper presents an eight transistor (8T) pico-watt current reference with a novel method of rectifying the prob-lem of exponential power increase w.r.t temperature in traditionalsub-nW references. The proposed current reference is obtainedby modifying the traditional beta-multiplier architecture to scale-down the power consumption without sacrificing area. Theconstancy of power consumption w.r.t temperature is achievedby exploiting the voltage-current characteristics of a leakagetransistor in the modified architecture. The proposed currentreference, implemented in UMC 55nm technology, occupies anarea of0.00035mm2. It is designed for a current of 60pA andachieves an accuracy of19ppm/0Cover a wide temperaturerange of−550Cto1250C. The reported line sensitivity for thecurrent reference is 0.07%/V in the supply range of 1.2V - 4V.Post-trim results show a constant power consumption of 144pWw.r.t temperature and process variations @1.2V supply.

Abstract

In this paper, we propose an accurate and computationally efficient Gradient Boosting approach for the estimation of statistical variations aware leakage power and propagation delay in the CMOS/FinFET standard digital cells. The proposed model estimates the leakage power and propagation delay w.r.t variations in process, temperature (−55°C to 125°C) and supply voltage(±10% variations). The distinguishing feature of the proposed approach is its compatibility with both CMOS and FinFET technologies. Moreover, the performance of the proposed model is consistent with various technology nodes. Exhaustive tests report an average error of <1% in 16nm CMOS and FinFET standard digital cells w.r.t analog HSPICE simulations with several orders increase in computational speed. Further, the complex cell estimation can be carried out through precharacterized standard cells abstaining longer simulations.