Inherent Uncertainty in the Determination of Multiple Event Cross Sections in Radiation Tests

In radiation tests on SRAMs or field-programmable gate arrays (FPGAs), two or more independent bitflips can be misled with a multiple event if they accidentally occur in neighbor cells. In the past, different tests, such as the “birthday statistics,” have been proposed to estimate the accuracy of the experimental results. In this article, simple formulas are proposed to determine the expected number of false 2- and 3-bit multiple cell upsets (MCUs) from the number of bitflips, memory size, and the method used to search multiple events. These expressions are validated using the Monte Carlo simulations and experimental data, and a technique is proposed to refine the experimental data and thus partially removing possible false events. Finally, it is demonstrated that there is a physical limit to determine the cross section of memories with arbitrary accuracy from a single experiment.