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Ōta-ku, Japan

Tanzawa T.,Micron Japan Ltd.
IEEE Transactions on Circuits and Systems II: Express Briefs | Year: 2011

This brief proposes an explicit Dickson charge pump model, including the effect of the resistance of switching devices on the pump performance. Using this model, one can estimate an optimum clock frequency and the size of the transferring transistors in terms of the main pump capacitors, the auxiliary capacitors, and the transfer transistors to maximize the output current under the same silicon area in a given technology. © 2011 IEEE. Source

Tanzawa T.,Micron Japan Ltd.
IEEE Transactions on Very Large Scale Integration (VLSI) Systems | Year: 2012

This brief discusses modeling of a high-voltage generator, including a charge pump circuit and a regulator for accelerating system-level simulations. Event-driven simulators become slow when hard switching frequently occurs to enable charge pump circuits even with a conventional model. A current mirror is added to the pump model and is connected to an output node of a comparator in the voltage detector to make every node in the feedback loop fully analog. Simulation results show that the simulation time for voltage generators' system is reduced by a factor of about 10 with an error of 5% in comparison with the conventional model. © 1993-2012 IEEE. Source

Tanzawa T.,Micron Japan Ltd.
Proceedings - IEEE International Symposium on Circuits and Systems | Year: 2015

This paper proposes an analytical, closed-form multi-sine AC-DC voltage multiplier model and investigates the dependency of input and output power on circuit and device parameters. Comparisons of the proposed model with SPICE simulation results are also provided for validation under various circuit parameters, such as the number of stages and capacitance per stage, and device parameters such as saturation current of diodes. The results suggest a voltage multiplier operating with a continuous wave is not less efficient than one operating with a multi-sine wave. This is in contrast to existing papers that show an entire system which includes both a voltage multiplier and rectenna is more efficient with a multi-sine wave than a continuous wave. © 2015 IEEE. Source

Torsi A.,Micron Technology Inc. | Zhao Y.,Micron Technology Inc. | Liu H.,Micron Technology Inc. | Tanzawa T.,Micron Japan Ltd. | And 3 more authors.
IEEE Transactions on Electron Devices | Year: 2011

We have developed a program-disturb model to characterize the channel potential of the program-inhibited string during nand flash cell programming. This model includes cell-to-cell capacitances from 3-D technology computer-aided design simulation and leakage currents associated with the boosted channel. We studied the program-disturb characteristics of sub-30-nm nand cells using a delayed programming pulse method. The simulation results agree with the experimental data very well and show quantitative impacts of junction leakage current, band-to-band tunneling (BTBT) current, Fowler-Nordheim tunneling current, and channel capacitance on the program disturb. We further discuss the cell-scaling trend and identify that the BTBT current can be a dominant mechanism for the program disturb of sub-20-nm nand cells. © 2010 IEEE. Source

Tanzawa T.,Micron Japan Ltd.
Proceedings - IEEE International Symposium on Circuits and Systems | Year: 2015

This paper proposes a comprehensive optimization methodology to simultaneously determine the clock frequency, area ratio of pump capacitor to switching circuit, number of stages, and capacitor size of integrated switched-capacitor charge pump voltage multipliers. Power efficiency of the charge pump is also discussed in various views. How the top and bottom plate parasitic capacitance and the threshold voltage of the switching circuit affect power efficiency is reviewed. The optimization methodology is demonstrated. Comparisons of the model with SPICE simulation results are also provided for validation. © 2015 IEEE. Source

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