Thermal Monitoring of Self-Checking Systems

With the increasing power density in integrated systems resulting from scaling down, the occurrence of field failures due to overheating has considerably increased. Faulty operation can be prevented by on-line temperature monitoring. This paper deals with questions of on-line temperature monitoring in safety-critical systems. First the possible temperature sensors are reviewed and basic principles of self-checking systems including such sensors are detailed, then a new temperature sensor cell with extremely good parameters designed especially for DfTT applications is presented. The basic questions of integrating thermal sensors into self-checking systems are also discussed.     

Reducing the effects of vegetation cover on airborne radiometric data using Landsat TM data

The gamma-ray spectrometry responses from bedrock in Canadian Shield areas are substantially masked by overburden and vegetation. Proper interpretation of airborne gamma-ray spectrometry data is dependent on accounting for the interference provided by surface cover. In this paper, a method is tested to correct airborne gamma-ray spectrometry, acquired over the Canadian Shield of northeastern Alberta, for vegetation screening by estimating the proportions of bedrock and vegetation cover from Landsat TM data. TM pixel values, due to the patchy network of bedrock and vegetation, result from a spectral mixture of these ground cover classes. Linear unmixing was implemented to deconvolve TM bands in abundance images to estimate proportions of bedrock and vegetation for each pixel. The outcrop abundance image, representing spatial variation in area percentage of bedrock, is used in linear regression analysis to calibrate co-registered K, eTh, and eU gamma-ray spectrometry channels to 40 per cent bedrock endmember images.     

Real-time heating and power characterization of cells in standard cell designs

In today's digital electronic integrated circuits device heating is one of the most critical issues. Overheating can cause failures in functionality and device malfunction. In certain circumstances overheating of ICs can cause physical destruction of the device itself. This paper introduces a solution to determine cell and gate heating curves across the standard cell IC's surface. The presented methodology and toolset is tightly integrated into standardized logic simulator engines thus providing digital circuit designers a low-level, cell-resolution temperature distribution map during logic simulations. Actual temperatures of each consisting cell of the design can be monitored throughout the whole logic simulation. By being able to monitor temperatures of digital cells during initial simulations, it allows us to detect hot-spots and overheating caused malfunctions far before manufacture. By using the spatial location and temperature magnitude of hot-spots acquired from the presented methodology, place and route (P&R) tools can be driven to change cell placement and routing in order to avoid heating caused failures. Additionally, cooling solutions can be developed using the simulated temperature maps of the IC's surface. This paper also presents various aspects of power characterization methods which were used throughout the experiments.     

Continuous analysis of dissolved gaseous mercury (DGM) and mercury flux in two freshwater lakes in Kejimkujik Park,Nova Scotia: evaluating mercury flux models with quantitative data

Diurnal patterns for dissolved gaseous mercury (DGM) concentration, mercury flux, several water variables (pH, oxidation reduction potential (ORP), water temperature), and meteorological variables (wind speed, air temperature, % relative humidity, solar radiation) were measured in two lakes with contrasting dissolved organic carbon (DOC) concentrations in Kejimkujik Park, Nova Scotia. A continuous analysis system made it possible to measure quick changes in DGM over time. Consistently higher DGM concentrations were found in the high DOC lake as compared to the low DOC lake. An examination of current mercury flux models using this quantitative data indicated some good correlations between the date and predicted flux (r ranging from 0.27 to 0.83) but generally poor fit (standard deviation of residuals ranging from 0.97 to 3.39). Cross-correlation analysis indicated that DGM dynamics changed in response to solar radiation with lag-times of 65 and 90 min. This relationship with solar radiation was used to develop new predictive models of DGM and mercury flux dynamics for each lake. We suggest that a generalized approach using time-shifted solar radiation date to predict DGM can be incorporated into existing mercury flux models. It is clear from the work presented that DOC and wind speed may also play important roles in DGM and mercury flux dynamics, and these roles have not been adequately accounted for in current predictive models.     

Temperature dependent timing in standard cell designs

This paper proposes a methodology to simulate temperature dependent timing in standard cell designs. Temperature dependent timing characteristics are derived from standard delay format (SDF) files that are created by synthesis tools automatically based on SPICE characterizations. In addition, a fast calculation of temperatures using the equivalent Foster RC network is presented. A case study is also presented in this paper where the temperature dependent frequency variation of a ring oscillator is simulated demonstrating the necessity of temperature dependent timing simulations. An adaptively refineable partitioning method for simulating standard cell designs logi-thermally is proposed as well. This paper also introduces recent enhancements in the CellTherm logi-thermal simulator developed in the Department of Electron Devices, BME, Hungary. Finally, the simulation results are compared and verified with the SPICE compatible ELDO analog simulator from Mentor Graphics.     

Tracing the thermal behavior of ICs

Today's increased power and packaging densities demand designers' attention to the effects of heat on ICs. The authors review thermal and electrothermal simulation and measurement methods, thermal package characterization, and the concept and techniques of design for thermal testability     

Increasing the accuracy of thermal transient measurements

Recent developments in the methodology of thermal transient measurements and evaluation are discussed in the paper. All of them are aimed at increasing the accuracy of these measurements and their evaluation. After a short summary of the evaluation methodology a procedure is presented for the correction of the nonconstant powering. New methods are presented for the compensation, evaluation and modeling of the nonlinearities. Various aspects of pulsed powering are discussed in detail.