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Creating optimal power designs involve making trade offs such as reliability-versus-power and area-versus- power at different stages of the design flow. Successful power-sensitive designs require engineers to have the ability to perform these trade offs accurately and efficiently. In order to achieve that, engineers require access to appropriate power analysis and optimization tools, which need to be integrated with the verification process of the system design.

The sheer amount of power consumed by some devices can cause significant design problems. For example, IC fan-out is determined by the amount of input current a gate load draws, and how much output current the driving gate can supply. In reality, a limit will be reached where a gate output cannot drive any more current into subsequent gate inputs; attempting to do so will cause the voltage to fall below the level defined for the logic level on that wire, resulting a failure in design. Another example: if the current across the resistor is increased by a fault design close to it’s maximum power rating, then the resistor will develop more voltage and therefore dissipate more power. This can cause overheating and burning of the area around the resistor, and in some cases cause the entire circuit to fail.

PCB designers try to design their circuit for specific voltage, current and threshold values for power dissipation, output current, junction temperature and frequencies. Being given these rated values, the designer chooses to adjust the design to minimize the stress on the components. This practice, known as "de-rating", is a technique through which either stresses acting on a part are reduced, or the strength of that part is increased by replacing it with a component with higher rated values. This analysis is usually performed by hand, and summarized in a spreadsheet format. fiXtress, however, can determine the applicable stress automatically under any EDA tool. Performing this analysis before the component’s placement and the manufacturing of the PCB, assures the proper component selection and saves redesign time, maximizing the circuit performance and reliability parameters.

To measure the electrical stress on each component in the design phase of an electrical circuit is not an easy task. Many parts have several parameters which must be assessed, including their electrical relation to adjacent components and to the entire circuit. For example, for a capacitor, working voltage as well as ripple current must be determined. For a resistor, it is power consumption as well as power-peak or voltage. For diodes, it may be reverse voltage, junction temperature, forward current and AC effects. The electrical stress information for all electrical circuit parts are fed into the fiXtress tool, which provides accurate power dissipation and thermal heat information on each component to meet reliable stress calculation and design requirements.

Optimal Parts:  

Enables to select the optimal rating of each component: for an overstressed component to select a higher rating value (larger physical size generates higher reliability), and for an under stressed component to select a lower rating value (smaller physical size saves PCB room).

Unlike standard Parts Count analysis, that uses a generic default for the stress applied to each component type, fiXtress uses the actual stress applied to each component. Components in equipment may not always operate under the reference conditions (parts count). In such cases, the real operational conditions will result in failure rates different from those given for reference conditions. To be able to follow accurate design criteria, fiXtress uses actual temperature and actual electrical stress imposed on each component. fiXtress increases system design reliability by using a four-stage analysis:

1. Performing comprehensive verification of circuit physical faults such as shorts and disconnections.

2. Complete analysis of the entire system stress characteristics, including temperature, frequencies, voltage, current, and power developed on each component and pin.

3. Comparing the stress results to de-rating curves to identify design faults. Recommendations to solve the stress problem are provided.

4. System MTBF prediction using a choice of industry standard methods to meet various environment requirements.

• Imports PCB Bill of Materials (BOM) and Netlist directly from all major CAD tools as well as Excel/CSV import
• Allows automatic IC data import from leading CAD and design tools
• Guides users through the entire simulation process, step-by-step, by means of a friendly online Buddy-Wizard
• Takes into consideration over 40 types of component groups
• Provides the current in each IC pin and connector pin
• Provides the current needed from each external power supply
• Designers can easily investigate power dissipation and operational current of voltage regulators and DC/DC converters used in the design with changing operation frequencies
• Can use results from Signal Integrity analysis to affect the stress caused by high frequency (above 200 MHz)
• Performs a high-edge profile analysis and finds worst-case scenarios
• Designed for quick and easy changes and updates of the PCB design
• Provides recommendations when over stress is detected
• Allows user-defined de-rating curves in addition to predefined de-rating curves
• Manages project trees, the core-database and HTML reports
• Predicts failure rates according to numerous standards allowing simulation of different environments (M217, M217+, IEC62380, Bellcore, HRD5, SN-29500 and FIDES)
• Provides optimization and curve sensitivity for Ambient/Case temperature, quality levels, environments and prediction methods.

SPICE normally simulates a model of a circuit at transistor level. These simulations must contain detailed information about the circuit and process parameters. Most IC vendors consider this type of information proprietary and resist making their models available to the public. Contrary to the SPICE models, fiXtress uses standard data sheets available to the public with no need for proprietary information. SPICE simulation accuracy is typically very good. However, simulation speeds are particularly slow for transient simulation analysis, which is most often used when evaluating power dissipation and signal integrity performance. fiXtress simulation speed is much faster than SPICE simulation, and allows what-if analysis very quickly.

Finally, not all SPICE simulators are fully compatible. Often, default simulator options are not the same in different SPICE simulators. Even though there are some very powerful options which control accuracy, convergence and the algorithm type, any options which are not consistent may cause poor correlation in results across different simulators. Moreover, because of the different variants of SPICE, these models are often incompatible between simulators; thus models must be extracted for a specific simulator.