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Abstract-In this paper, a new dynamic reference scheme is proposed to improve the read voltage margin better than the previous static reference scheme. The proposed dynamic reference scheme can be helpful in compensating not only the background pattern dependence but also the cell position dependence. The proposed dynamic reference is verified by simulating the CMOS-memristor hybrid circuit using the practical CMOS SPICE and memristor Verilog-A models. In the simulation, the percentage read voltage margin is compared between the previous static reference scheme and the new dynamic reference scheme. Assuming that the critical percentage of read voltage margin is 5%, the memristor array size with the dynamic scheme can be larger by 60%, compared to the array size with the static one. In addition, for the array size of 64 x 64, the interconnect resistance in the array with the dynamic scheme can be increased by 30% than the static reference one. For the array size of 128 x 128, the interconnect resistance with the proposed scheme can be improved by 38% than the previous static one, allowing more margin on the variation of interconnect resistance.Index Terms-Dynamic reference scheme, read voltage margin, cell-position and background-pattern dependencies, pure memristor array

Abstract:In this paper, we propose a reconfigurable charge pump (RCP) circuit that could change its architecture according to sunlight variation. In strong sunlight, the RCP works by the parallel mode that can maximize the output current. In moderate sunlight, the RCP changes to the serial-parallel mode. When sunlight becomes weak, the RCP runs by the serial mode to keep its output voltage around the target voltage. Compared with the fixed-mode circuit that maintains the serial mode all the time regardless of sunlight variation, the RCP can generate 2.5 times larger output current and has power efficiency better by 24%, in strong sunlight. The area penalty and overhead in power efficiency of the RCP are only 15.8% and 1.2%.

Sunlight is one of useful energy harvesting sources that can be found everywhere. In spite of this ubiquitous availability, sunlight intensity is dynamically changing. Thus Maximum Power Point Tracking (MPPT) circuits are needed to harvest the maximum available energy from the solar cell, regardless of sunlight intensity variation. In this paper, three charge pump circuits for solar energy harvesting are discussed in terms of the output current and energy efficiency. The first charge pump can change its pumping frequency to track the maximum power point at a given sunlight condition. The second circuit can reconfigure its architecture according to the sunlight variation to maximize its output current with varying the sunlight intensity. In the third pump circuit, the reconfigurable architecture can be combined with the variable pumping frequency to keep the power efficiency high at any sunlight condition.

Abstract-For some low-frequency applications such as power-related circuits, NEM relays have been known to show better performance than MOSFETs. For example, in a step-down charge pump circuit, the NEM relays showed much smaller layout area and better energy efficiency than MOSFETs. However, severe process variations of NEM relays hinder them from being widely used in various low-frequency applications. To mitigate the process-variation problems of NEM relays, in this paper, a new NEMrelay charge pump circuit with the self-adjustment is proposed. By self-adjusting a pulse amplitude voltage according to process variations, the power consumption can be saved by 4.6%, compared to the conventional scheme without the self-adjustment. This power saving can also be helpful in improving the power efficiency of the proposed scheme. From the circuit simulation of NEM-relay charge pump circuit, the efficiency of the proposed scheme is improved better by 4.1% than the conventional.