Programmable chip maker Actel (distributed by Soanar ) has released the results of a “comprehensive third-party investigation” into the effects of high-energy neutrons generated by cosmic rays striking the Earth’s atmosphere*. According to the company, the report verifies that field-programmable gate arrays (FPGAs) based on Flash and antifuse technologies are immune to configuration upsets caused by the neutrons.
In addition, the study, produced by iRoC Technologies at the Los Alamos Neutron Sciences Center in the US, determined that SRAM-based FPGAs are vulnerable to neutron-induced configuration loss not only under high-altitude conditions, as traditionally believed, but also in ground-based applications. SRAM-based FPGAs are a popular architecture among leading programmable device manufacturers.
iRoC conducted a series of tests to determine the failure rate of five different FPGA architectures, including Actel’s antifuse-based Axcelerator FPGA and Flash-based ProASIC Plus devices and several SRAM-based FPGAs.
According to the report, the testing demonstrated that antifuse- and Flash-based FPGAs suffered no loss of configuration under neutron bombardment while the tested SRAM-based FPGAs demonstrated a failures in time (FIT) rate ranging from 1,150 at sea level to 3,900 at 5,000 feet (1525 m) to 540,000 at 60,000 feet (18,300 m). One FIT is defined as one failure in 109 hours. While ICs typically have FIT rates lower than 100, high-reliability applications require a FIT rate of 10 to 20.
The tests, which followed the US industry-prescribed JESD-89 test methodology, were conducted in February 2004.
“As a third party test house, we use a consistent, high quality methodology so results can be compared with confidence,” states Olivier Lauzeral, Director of US Operations at iRoC Technologies. “We confirmed that SRAM technology is much more susceptible to soft errors than all other technologies tested.
“When high-energy neutrons penetrate memory cells, such as those used in SRAM-based programmable logic devices, it is highly probable that functional failure will cause the device to operate in an unpredictable manner. This can be detrimental to systems we rely on every day, such as the telephone network, automotive airbags, medical equipment and even military and aerospace applications,” concludes Lauzeral.
*The results of the study are documented in “Radiation Results of SER (Soft-Error Rate) Test of Actel, Xilinx and Altera FPGA Instances”. See www.actel.com/products/rescenter/ser/index.html