Safety Analysis For Integrated Circuits In The Context Of Hybrid Systems

Many real-life systems have integrated circuits interacting with physical systems in safety critical applications. These systems are called hybrid systems. The safety analysis of integrated circuits used in such systems is typically done in isolation of the end application and associated physical system, and hence results in the need to take recourse to conservative design techniques utilizing costly redundancy. We are gradually moving away from the paradigm of independently designing the digital and physical parts of hybrid systems towards simultaneous considerations for both. These systems have an acceptable tolerance determined by the application due to the inertial nature of the physical system, error tolerance capability in closed loop applications, built-in hardware and software functionality, etc. In this paper, we perform a comparative study of integrated circuit safety analysis as practiced today and system level application specific safety analysis that incorporates a physical system. We propose an improved method based upon the divide and conquer approach for such co-analysis to address practical limitations associated with adopting system level analysis techniques during integrated circuit design. Experimental results for a representative motor control system indicate that the application has an error tolerance of 92-160 cycles of closed loop operation for worst case errors and a control value error tolerance in the range of 5-7% at different operating conditions. Incorporation of application tolerance results in up to 4.3X reduction in the number of hardware elements which need to be protected.