Vivian A. Bartlett

Investigation of stepwise charging circuits for power-clock generation in Adiabatic Logic

The generation of power-clocks in adiabatic integrated circuits is investigated. Specifically, we consider stepwise charging strategies (2, 3, 4, 5, 6, 7, and 8-step) based on tank-capacitor circuits, comparing them in terms of their energy recovery properties and complexity. We show that energy recovery achievable depends on the tank-capacitor size. We also show that tank-capacitor sizes can be reduced as their number increases concluding that combined tank capacitance (CTT) versus load capacitance (CL) ratio is the significant parameter. We propose that using a CTT/CL ratio of 10 and using a 4-step charging power-clock constitute appropriate trade-offs in practical circuits.

4-phase resettable quasi-adiabatic flip-flops and sequential circuit design

Resettable adiabatic flip-flops are essential in the design of adiabatic counters, thus, a comprehensive study for IECRL, PFAL and EACRL 4-phase quasi-adiabatic logic families have been done in this paper. In addition, a new resettable quasi-adiabatic flip-flop circuit is proposed for each of them. Using the non-resettable and the proposed resettable adiabatic flip-flops, a practical sequential circuit comprising of a 2-bit twisted ring counter is designed and the energy consumption, for four distinct states, at different ramping times is measured. The simulation results show that the energy consumption of the resettable counter is comparable with its non-resettable counterparts. Moreover, amongst the adiabatic logic used, the PFAL based implementation of both the non-resettable and the resettable counters exhibits the least energy consumption at all ramping times.

Energy efficient implementation of multi-phase quasi-adiabatic Cyclic Redundancy Check in near field communication

Abstract Ultra-low power operation in power-limited portable devices (e.g. cell phone and smartcard) is paramount. Existing conventional CMOS consume high energy. The adiabatic logic technique has the potential of rendering energy efficient operation. In this paper, a multi-phase quasi-adiabatic implementation of 16-bit Cyclic Redundancy Check (CRC) is proposed, compliant with the ISO/IEC-14443 standard for contactless smart cards. In terms of a number of CRC bits, the design is scalable and all generator polynomials and initial load values can be accommodated. The CRC design is used as a vehicle to evaluate a range of adiabatic logic styles and power-clock strategies. The effects of voltage scaling and variations in Process-Voltage-Temperature (PVT) are also investigated providing an insight into the robustness of adiabatic logic styles. PFAL and IECRL designs using a 4-phase power-clock are shown to be both the most energy-efficient and robust designs.

Energy efficiency of 2-step charging power-clock for adiabatic logic

The generation of power-clocks in adiabatic integrated circuits is investigated. Specifically, we consider the energy efficiency of a 2-step charging strategy based on a single tank-capacitor circuit. We have investigated the impact of various parameters such as tank-capacitance to load capacitance ratio, ramping time, transistors sizing and power supply voltage scaling on energy recovery achievable in the 2-step charging circuit. We show that energy recovery achievable in the 2-step charging circuit depends on the tank-capacitor and load capacitor size concluding that tank-capacitance (CT) versus load capacitance (CL) is the significant parameter. We also show that the energy performance depends on the ramping time and improves for higher ramping times (lower frequencies). Energy recovery also improves if the transistors sizes in the step charging circuit are sized at their minimum dimensions. Lastly, we show that energy recovery decreases as the power supply voltage is scaled down. Specifically, the decrease in the energy recovery with decreasing power supply is significant for lower ramping times (higher frequencies). We propose that a Ct/Cl ratio of 10, keeping the width of the transistors in the step charging circuit minimum, can be chosen as a convenient ‘rule-of-thumb’ in practical designs.

Robustness of power analysis attack resilient adiabatic logic: WCS-QuAL under PVT variations

In this paper, we propose Without Charge Sharing Quasi Adiabatic Logic (WCS-QuAL) as a countermeasure against Power Analysis Attacks. We evaluate and compare our logic with the recently proposed secure adiabatic logic designs SPGAL and EE-SPFAL at frequencies ranging from 1MHz to 100MHz. Simulation results show that WCS-QuAL outperforms the existing secure adiabatic logic designs on the basis of % Normalized Energy Deviation (NED) and % Normalized Standard Deviation (NSD) at all simulated frequencies. Also, all 2-input gates using WCS-QuAL dissipate nearly equal energy for all possible input transitions. In addition, the energy dissipated by WCS-QuAL approaches to the energy dissipation of EE-SPFAL and SPGAL as the output load capacitance is increased above 100fF. To further evaluate and compare the performance, GF (24) bit-parallel multiplier was implemented as a design example. The impact of Process-Voltage-Temperature (PVT) variations, power supply scaling and technology on the performance of the three logic designs was investigated and compared. Simulation results show that WCS-QuAL passed the functionality test against PVT variations and can perform well against the power supply scaling (from 1.8V to 0.5V). It also exhibits the least value of %NED and %NSD against PVT variations and when the power supply is scaled down compared to EE-SPFAL and SPGAL. At lower technology, WCS-QuAL, shows more improvement in energy dissipation than EE-SPFAL.

Adiabatic flip-flops and sequential circuit design using novel resettable adiabatic buffers

We propose novel resettable adiabatic buffers for five adiabatic logic families namely; Efficient Adiabatic Charge Recovery Logic (EACRL), Improved Efficient Charge Recovery Logic (IECRL), Positive Feedback Adiabatic Logic (PFAL), Complementary Pass-transistor Adiabatic Logic (CPAL) and Clocked Adiabatic Logic (CAL). We present the design of resettable flip-flops using the proposed buffers. The proposed flip-flops alleviate the problem of increased energy and area consumption incurred by the existing mux-based resettable flip-flops. We then design the 3-bit up-down counters and extended our comparison beyond energy dissipation using the above five adiabatic logic families. PFAL based sequential circuit designs gives the best performance trade-offs in terms of complexity, energy, speed and area compared to the other adiabatic designs.