Yasuyuki Matsuya

1-V power supply high-speed digital circuit technology with multithreshold-voltage CMOS

1-V power supply high-speed low-power digital circuit technology with 0.5-/spl mu/m multithreshold-voltage CMOS (MTCMOS) is proposed. This technology features both low-threshold voltage and high-threshold voltage MOSFETs in a single LSI. The low-threshold voltage MOSFETs enhance speed performance at a low supply voltage of 1 V or less, while the high-threshold voltage MOSFETs suppress the stand-by leakage current during the sleep period. This technology has brought about logic gate characteristics of a 1.7-ns propagation delay time and 0.3-/spl mu/W/MHz/gate power dissipation with a standard load. In addition, an MTCMOS standard cell library has been developed so that conventional CAD tools can be used to lay out low-voltage LSIs. To demonstrate MTCMOSs effectiveness, a PLL LSI based on standard cells was designed as a carrying vehicle. 18-MHz operation at 1 V was achieved using a 0.5-/spl mu/m CMOS process. >

A 1-V multithreshold-voltage CMOS digital signal processor for mobile phone application

A 1-V power supply low-power and high-speed 16-b fixed-point digital signal processor using a 0.5-/spl mu/m process has been developed for mobile phone applications. A 1-V multithreshold-voltage CMOS (MTCMOS) technology that uses both high-threshold-voltage and low-threshold-voltage transistors is one key to attaining low power consumption, keeping processing throughput high. A maximum operating frequency of 13.2 MHz and an energy consumption of 2.2 mW/MHz were achieved at 1 V. The second key to low-power operation is a power management scheme that uses a secondary embedded microprocessor. This proposed scheme minimizes the standby power in the waiting state by effectively controlling the sleep mode in the MTCMOS design. We confirmed that the standby leakage current was reduced three orders of magnitude and that the energy consumed in the waiting state was less than 1/10 of that consumed by conventional CMOS circuits with lowered supply voltage and threshold voltage but without power management.

A 1-V high-speed MTCMOS circuit scheme for power-down applications

A new MTCMOS concept is proposed for power-down applications. This concept realises a new circuit scheme to hold data during the power-down period in which the power is not supplied. Low-power, high-speed performance are achieved by separating the holding circuit from the critical path. A scan register has been developed based on this concept. Using this scheme for an LSI chip, 20-MHz operation at 1.0 V and only a few nA standby current was achieved with 0.5-/spl mu/m CMOS technology.

Power management technique for 1-V LSIs using embedded processor

A new power management technique is proposed for low-power, high-speed LSIs. This technique reduces the power consumption and enhances the performance of an LSI by using an embedded small processor to control the sleep modes and the processing of the LSI. Using this technique for a low-power DSP, the total power is reduced to about 10% of one without this technique, while maintaining the speed performance in 1-V LSIs.

Optical Wireless Digital-Sound Transmission System With 1-Bit

Spherical Si solar cells (diameter of 1 mm) with a reflector cup (diameter of 2.2 mm) were used with 1-bit ΔΣ-modulated illumination from white LEDs to provide optical wireless digital-sound transmission. The solar cells have a high directivity with regard to incident light, thus largely eliminating the environmental noise from fluorescent lighting. An optical wireless transmission system consists of a transmitter and a receiver. The transmitter contains a battery-operated lamp with 50 white LEDs and a 1-bit ΔΣ modulator that controls the current to the lamp. The receiver consists of just a spherical-solar-cell module and an earphone. In the experiment, the transmitter converted a 1-kHz analog signal into digital pulses at a sampling frequency of 1 MHz and sent the digital data over a distance of 50 cm at an illumination of 70 lx. The measured output spectrum of the receiver showed that it recreated a sinusoidal waveform with little distortion. Even under fluorescent lighting with an illumination of 200 lx, the measured spectrum showed that a sinusoidal waveform with a signal-to-peak-noise ratio of 25 dB was obtained.

\Delta \Sigma

Limit-cycle oscillation in noise-shaping D/A converters is one of serious problems because it interrupts their noise-shaping operation. We propose a new noise-shaping structure that prevents limit-cycle oscillation. We have used this structure in an audio D/A converter that we fabricated. The measured result shows that limit-cycle oscillation is prevented and noise-shaping operation is maintained even when the input data is real zero. This D/A converter achieves the S/N+THD of 101 dB.

-Modulated Visible Light and Spherical Si Solar Cells

The chaotic delta sigma modulator is a way to suppress the limit cycle oscillation caused by the input of a null or constant signal. By changing integrator gains, the output sequence becomes chaotic and the noise characteristic of the output is changed. This noise characteristic is an important factor for evaluating the performance of delta sigma modulation. The aim of this study is to analyze the noise characteristic of chaotic double loop delta sigma modulation when the null signal is input. We use a bifurcation diagram and FFT analysis to obtain the parameter dependence of the output state and noise characteristic, respectively. The output status of the chaotic double loop delta sigma modulation can be guessed from a bifurcation diagram with the brute force method. We also investigate the noise characteristic of the output signal of the chaotic modulator with FFT analysis and classify the various noise characteristics by changing the integrator gains of the double loop delta sigma modulator. We use FFT and the bifurcation diagram to classify these noise characteristics into three categories: suppressed tone (affected by the chaos), divergence, and the appearance of the limit cycle oscillation. We also confirm the existence of an unusual noise-shaping characteristic caused by the intermittent chaos.

A 4th-order local-feedforward D/A converter that prevents limit-cycle oscillation

Techno-stress has been a problem in recent years with a development of information technology. Various studies have been reported about a relationship between key typing and psychosomatic state. Keystroke dynamics are known as dynamics of a key typing motion. The objective of this paper is to clarify the mechanism between keystroke dynamics and physiological responses. Inter-stroke time (IST) that was the interval between each keystroke was measured as keystroke dynamics. The physiological responses were heart rate variability (HRV) and respiration (Resp). The system consisted of IST, HRV, and Resp was applied multidimensional directed coherence in order to reveal a causal correlation. As a result, it was observed that strength of entrainment of physiological responses having fluctuation to IST differed in surround by the noise and a cognitive load. Specifically, the entrainment became weak as a cognitive resource devoted to IST was relatively increased with the keystroke motion had a robust rhythm. On the other hand, the entrainment became stronger as a cognitive resource devoted to IST was relatively decreased since the resource also devoted to the noise or the cognitive load.

Noise characteristic of the chaotic double loop delta sigma modulator

The objective of this paper is to clarify the interrelation between vehicle operating data and physiological responses to different psychological states. Multidimensional directed coherence (MDC) analysis was applied to the human–machine system, as observed by vehicle operating data and physiological indices to reveal the mechanism of the interrelation. The MDC analysis is one way to visualize the information flow between an arbitrary number of time series signals in the frequency domain. As a result, it was found that the entrainment of physiological indices on vehicle operating data is different depending on the cognitive resources devoted to driving motion. In particular, it was clarified that driving motion is easily influenced by physiological indices when the cognitive resources devoted to driving motion are few either absolutely or relatively.

Multidimensional directed coherence analysis of keystroke dynamics and physiological responses

Spherical Si solar cells (diameter: 1 mm) with a reflector cup (diameter: 2.2 mm) were used with 1-bit SigmaDelta-modulated illumination from white LEDs to provide optical wireless digital-sound transmission. The solar cells have a high directivity with regard to incident light, thus largely eliminating the environmental noise from fluorescent lighting. To verify the effectiveness of our optical, wireless digital sound transmission scheme, we fabricated an experimental system consisting of a transmitter and a receiver. The transmitter contains a battery-operated lamp with 50 white LEDs and a 1-bit SigmaDelta modulator that controls the current to the lamp. The receiver consists of a spherical-solar-cell module and an earphone. In the experiment, the transmitter produced a 1-kHz analog signal at an illumination of 70 1x that traveled over a distance of 50 cm. The measured output spectrum of the receiver showed that it recreated a sinusoidal waveform with little distortion. Even under fluorescent lighting with an illumination of 200 1x, the measured spectrum showed that a sinusoidal waveform with a signal-to-peak-noise ratio of 25 dB was obtained.