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[Author] Kousuke MIYAJI(5hit)

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  • Initialize and Weak-Program Erasing Scheme for High-Performance and High-Reliability Ferroelectric NAND Flash Solid-State Drive

    Kousuke MIYAJI  Ryoji YAJIMA  Teruyoshi HATANAKA  Mitsue TAKAHASHI  Shigeki SAKAI  Ken TAKEUCHI  

     
    PAPER

      Vol:
    E95-C No:4
      Page(s):
    609-616

    Initialize and weak-program erasing scheme is proposed to achieve high-performance and high-reliability Ferroelectric (Fe-) NAND flash solid-state drive (SSD). Bit-by-bit erase VTH control is achieved by the proposed erasing scheme and history effects in Fe-NAND is also suppressed. History effects change the future erase VTH shift characteristics by the past program voltage. The proposed erasing scheme decreases VTH shift variation due to history effects from ±40% to ±2% and the erase VTH distribution width is reduced from over 0.4 V to 0.045 V. As a result, the read and VPASS disturbance decrease by 42% and 37%, respectively. The proposed erasing scheme is immune to VTH variations and voltage stress. The proposed erasing scheme also suppresses the power and bandwidth degradation of SSD.

  • Analysis of Operation Margin and Read Speed in 6T- and 8T-SRAM with Local Electron Injected Asymmetric Pass Gate Transistor

    Kousuke MIYAJI  Kentaro HONDA  Shuhei TANAKAMARU  Shinji MIYANO  Ken TAKEUCHI  

     
    PAPER

      Vol:
    E95-C No:4
      Page(s):
    564-571

    Three types of electron injection scheme: both side injection scheme and self-repair one side injection scheme Type A (injection for once) and Type B (injection for twice) are proposed and analyzed comprehensively for 65 nm technology node 6T- and 8T-SRAM cells to find the optimum injection scheme and cell architecture. It is found that the read speed degrades by as much as 6.3 times in the 6T-SRAM with the local injected electrons. However, the read speed of the 8T-SRAM cell does not degrade because the read port is separated from the write pass gate transistors. Furthermore, the self-repair one side injection scheme is most suitable to solve the conflict of the half select disturb and write characteristics. The worst cell characteristics of Type A and Type B self-repair one side injection schemes were found to be the same. In the self-repair one side injection 8T-SRAM, the disturb margin increases by 141% without write margin or read speed degradation. The proposed schemes have no process or area penalty compared with the standard CMOS-process.

  • A 65nm CMOS Process Li-Ion Battery Charging Cascode SIDO Boost Converter with 89% Maximum Efficiency for RF Wireless Power Transfer Receiver

    Yasuaki ISSHIKI  Dai SUZUKI  Ryo ISHIDA  Kousuke MIYAJI  

     
    PAPER-Electronic Circuits

      Pubricized:
    2020/04/22
      Vol:
    E103-C No:10
      Page(s):
    472-479

    This paper proposes and demonstrates a 65nm CMOS process cascode single-inductor-dual-output (SIDO) boost converter whose outputs are Li-ion battery and 1V low voltage supply for RF wireless power transfer (WPT) receiver. The 1V power supply is used for internal control circuits to reduce power consumption. In order to withstand 4.2V Li-ion battery output, cascode 2.5V I/O PFETs are used at the power stage. On the other hand, to generate 1V while maintaining 4.2V tolerance at 1V output, cascode 2.5V I/O NFETs output stage is proposed. Measurement results show conversion efficiency of 87% at PIN=7mW, ILOAD=1.6mA and VBAT=4.0V, and 89% at PIN=7.9mW, ILOAD=2.1mA and VBAT=3.4V.

  • Design and Integration of Beyond-10MHz High Switching Frequency DC-DC Converter Open Access

    Kousuke MIYAJI  

     
    INVITED PAPER

      Pubricized:
    2022/04/20
      Vol:
    E105-C No:10
      Page(s):
    521-533

    There are continuous and strong demands for the DC-DC converter to reduce the size of passive components and increase the system power density. Advances in CMOS processes and GaN FETs enabled the switching frequency of DC-DC converters to be beyond 10MHz. The advancements of 3-D integrated magnetics will further reduce the footprint. In this paper, the overview of beyond-10MHz DC-DC converters will be provided first, and our recent achievements are introduced focusing on 3D-integration of Fe-based metal composite magnetic core inductor, and GaN FET control designs.

  • A Temperature Tracking Read Reference Current and Write Voltage Generator for Multi-Level Phase Change Memories

    Koh JOHGUCHI  Toru EGAMI  Kousuke MIYAJI  Ken TAKEUCHI  

     
    PAPER

      Vol:
    E97-C No:4
      Page(s):
    342-350

    This paper gives a write voltage and read reference current generator considering temperature characteristics for multi-level Ge2Sb2Te5-based phase change memories. Since the optimum SET and RESET voltages linearly changes by the temperature, the voltage supply circuit must track this characteristic. In addition, the measurement results show that the read current depends on both read temperature and the write temperature and has exponential dependence on the read temperature. Thus, the binning technique is applied for each read and write temperature regions. The proposed variable TC generator can achieve below ±0.5 LSB precision from the measured differential non-linearity and integral non-linearity. As a result, the temperature characteristics of both the linear write voltage and the exponential read current can be tracked with the proposed variation tolerant linear temperature coefficient current generator.

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