1.6. Failure Rates
For example, a design with 5,000 FIT experiences a mean of 5,000 SEU events in 109 hours (114,155.25 years). Because SEU events are statistically independent, FIT is additive. If a single FPGA has 5,000 FIT, then ten FPGAs have 50,000 FIT (50,000 failures in 114,155.25 years).
Another reliability measurement is the mean time to failure (MTTF), which is the reciprocal of the FIT or 1/FIT. For a FIT of 5,000 in standard units of failures per billion hours, MTTF is 1/(5,000/1Bh) = 1 billion/5,000 = 200,000 hours = 22.83 years.
SEU events follow a Poisson distribution, and the cumulative distribution function (CDF) for mean time between failures (MTBF) is an exponential distribution. For more information about failure rate calculation, refer to the Intel® FPGA Reliability Report (available upon request).
Neutron SEU incidence varies by altitude, latitude, and other environmental factors. The Intel® Quartus® Prime software provides SEU FIT reports based on compiles for sea level in Manhattan, New York. The JESD89A specification defines the test parameters.