A possible approach for determining safety parameters for safety integrated circuits

The approach for calculating the failure rate of a safety integrated circuit is used if the number of available test patterns is not sufficient. The safety integrated circuit can be structured in function blocks, that can be functionally compared to semiconductors with discrete structure. Failure models already known and applied for discrete semiconductors can be used to determine the failure rate of the individual function blocks. These models with their known failure rates serve as a reference for the safety integrated circuit function blocks. An advantage of this approach is that the internal safety integrated circuit structure can be taken into consideration when calculating the failure probability. The paper is based on the principles of the generic standard IEC 61508 Edition 2, 2010-04. Because new technologies lack field experience and a basis for evaluating certain risks, a conservative approach to determining failure rates has been emphasized as set forth in SN 29500.