Abstrucf-Recent research has demonstrated that for certain types of applications like sampled audio systems, self-timed circuits can achieve very low power consumption, because unused circuit parts automatically turn into a stand-by mode. Additional savings may be obtained by combining the self-timed circuits with a mechanism that adaptively adjusts the supply voltage to the smallest possible, while maintaining the performance requirements. This paper describes such a mechanism, analyzes the possible power savings, and presents a demonstrator chip that has been fabricated and tested. The idea of voltage scaling has been used previously in synchronous circuits, and the contributions of the present paper are: 1) the combination of supply scaling and self-timed circuitry which has some unique advantages, and 2) the thorough analysis of the power savings that are possible using this technique.
The Joint Committee for Guides in Metrology, Working Group 1, JCGM-WG1, is currently revising the ‘Guide to the Expression of Uncertainty in Measurement’. In this communication, the motivation for undertaking such a revision is given and the main changes with respect to the current, 2008 edition are outlined.
This paper addresses the design of asynchronous circuits for low power through an example: a filter bank for a digital hearing aid. The asynchronous design re-implements an existing synchronous circuit which is used in a commercial product. For comparison, both designs have been fabricated in the same 0.7-m CMOS technology. When processing typical data (less than 50-dB sound pressure), the asynchronous design consumes 85 W-a fivefold reduction compared to the synchronous design. This has been achieved by the use of asynchronous control and data-path logic, an improved RAM design, and by a mechanism that adapts the number range to the actual need (exploiting the fact that typical audio signals are characterized by numerically small samples). Apart from the improved RAM design, these measures are only viable in an asynchronous design. The principles and techniques explained in this paper are of a general nature, and they apply to the design of asynchronous low-power digital signal-processing circuits in a broader perspective. In fact, this understanding is one of the contributions of the paper. Finally, the paper can be read as an example-driven introduction to asynchronous low-power design.
Articles you may be interested inCompact ultra-fast vertical nanopositioner for improving scanning probe microscope scan speed Rev. Sci. Instrum. 82, 123703 (2011); 10.1063/1.3664613 Quantitative scanning probe microscope topographies by charge linearization of the vertical actuator Rev. Sci. Instrum. 81, 103701 (2010); 10.1063/1.3488359Wideband and hysteresis-free regulation of piezoelectric actuator based on induced current for high-speed scanning probe microscopy Rev.Most scanning probe microscopes use piezoelectric actuators in open loop configurations. Therefore a major problem related to these instruments is the image distortion due to the hysteresis effect of the piezo. In order to eliminate the distortions, cost effective software control based on a model for hysteresis can be applied to the scanner. We describe a new rate-independent model for the hysteresis of a piezo scanner. Two reference standards were used to determine the accuracy of the model; a one-dimensional grating with a period of 3.0 m and a two-dimensional grating with 200 nm pitch. The structures were scanned for different scan ranges varying from 5 V peak to peak to 440 V peak to peak, so that 99% of the scanners' full motion range was covered. A least-squares fit of the experiments to the hysteresis model provided standard deviations per scan range of around 0.2%. This represents an uncertainty of 1 pixel. Since our model is based on a differential equation, it is flexible even to simulate arbitrary experimental conditions such as a sudden change in the offset.
There is an increasing demand for accurate and traceable measurements with atomic force microscopes (AFMs) within many fields, such as micro optics where the functionality of components is directly and critically related to the absolute dimensions. In particular, true three-dimensional measurements of deep structures, that is, structures with a dept larger than the width, are a challenge. This chapter is a contribution to setting up guidelines for the three-dimensional calibration of so-called closed loop atomic force microscopes, where distance sensors such as capacitive sensors measure the movement of the tip. In earlier published works, the calibration along the axes has been derived but often the coupling between the horizontal and vertical movements, which has to be known in order to make a true three-dimensional measurement, has not been assessed. In this chapter, a thorough analysis describes the "true" metric x-, y-, and z-coordinates of an imaged surface as a linear function of the observed xl-, yl-, and zl-coordinates, taking into account the coupling between the horizontal and vertical movements. Based on series of measurements on triangularly shaped ridges, an analytical model function for the two coefficients describing this coupling is given. The misalignment of the vertical axes relative to the horizontal axes was found to be 1.0(0.2)h and 2.7(0.2)h for the investigated closed loop AFM. Ignoring the influence of the tip shape, it is now possible with our setup to correct any image of a three-dimensional surface. An example of estimating the technological important sidewall angle a of a grating wall with an uncertainty of u(a) z 0.3h is given.
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