Engineers design for system-level reliability when creating complex electronic systems. System reliability is dependent on a number of factors, including the reliability of the individual semiconductor devices selected for each design. Radiation effects impact device reliability in terrestrial applications, and by choosing FPGA components judiciously, designers can significantly enhance the operational reliability and stability of any system.

Natural background radiation has a number of sources, including cosmic rays originating outside our solar system, charged particles streaming out from our sun in the solar wind, and terrestrial radioactive decay of materials relatively abundant in our earthbound environment. As solar wind particles interact with Earth’s atmospheric gases, they produce showers of neutrons that reach the Earth’s surface. Neutron counts at sea level vary inversely with the 11-year sunspot cycle. In 2007 the sun was approaching a new sunspot minimum, with expectations that sunspot counts would begin to increase in 2008. This has not yet happened. As of August 2009, the sunspot count has been at or near zero for the past 12 months, and sea-level neutron flux measurements are now well past the previous maximum readings measured in 1965, with predictions of even higher peak readings.

Also of concern are alpha particles emitted by isotopes present even in the low-alpha plastic molding compounds used in semiconductor packaging. Because these materials are in close proximity to the semiconductor die, package-originated alpha particle effects are impossible to avoid.

With the ambient neutron flux rising well past previous maximum counts over the last 45 years, and with the unavoidable exposure to alpha particles from within semiconductor packaging itself, it is critical for engineers to have an understanding of the real-world effects that these particles have on common FPGA device types. This article examines these effects for SRAM FPGAs, explores the difference between soft and firm errors, looks at FPGA firm-error immunity, and details third-party alpha and neutron testing results for a wide range of FPGA architectures.

As reliability requirements for ground-based systems increase, and as the terrestrial operating environment becomes more challenging, these effects are much more relevant to system designers. By carefully choosing FPGA devices, designers can ensure they deliver highly reliable systems that can operate even in the most challenging extended availability ground-based applications.

To download this paper, click here.

Tags: Actel

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