Exploring design diversity redundancy to improve resilience in mixed-signal systems

• Design Diversity is a feasible technique that may be used to increase reliability in mixed signal redundant systems.
• Mixed Signal Design Diversity (MS-DDR) allows the redundancy application in distinct domains and abstraction levels.
• Hardware and temporal diversity in A/D interfaces, with spatial temporal voting, increase the tolerance to multiple faults.
• Mixed signal diversity schemes require synchronizer blocks and flexible voters.
• Current mixed signal programmable devices allow the application of MS-DDR with virtually zero area overhead.

Redundancy is the most popular technique to add fault tolerance at system level to electronic systems. Redundancy with hardware and software diversity of digital computers is currently employed in safety critical applications, as, for example, in spacecrafts and commercial aircrafts, to increase the reliability of such systems. This work presents a study of the design diversity redundancy technique in the context of mixed-signal systems, identifying the advantages and associated costs of applying this technique to subsystems with both analog and digital parts. The discussion is based on three case studies: two data acquisition systems and a low-pass filter, all of them prototyped in mixed-signal programmable platforms. In these systems, different combinations regarding the number of modules (double or triple modular redundancy) and specific issues related to the applied diversity modes are considered. Based on the results of fault injection campaigns by hardware emulation and one neutron irradiation test, the achieved reliability level of each studied system is discussed, as well as the tradeoffs of applying design diversity redundancy to mixed-signal systems.