Research On Some Problems About Fault Diagnosis System Of Mixed-signal Circuit

With the fast development of electronic technology, the complexity of electro circuits system increases sharply. Nowadays more and more chips (some 60%) contain both digital and analog signal simultaneously, resulting in a greater difficulty in circuits testing. However, the Discrete Event System (DES) theory proposes a mathematical model applicable for most mixed-signal circuits testing and fault diagnosis, gives out a solution to the main difficulties concerned to a certain extent. This thesis focuses on the key problems with fault diagnosis of mixed-signal circuit under the instruction of DES theory.This thesis is based on my R&D work done, mainly includes: Careful research in circuits fault diagnosis model based on DES theory, as well as analysis of the superiority and shortage of the theory. A new proposal to the computing of minimal testing set in view of it's great difficulty in circuits testing process based on DES theory, which utilizes linear equations group to convert the computing task into a simple process of wiping off redundant equations, solving the problem in an algebra way. This paper studies some algorithms of computing the minimal test set of circuits, expounds the algorithms' thoughts, analyzes their advantages and- shortcomings. A complete practice on a circuit fault diagnosis under the instruction of the theory, as well as an analysis on the circuits testing costs. In the diagnosis and analysis process, the plug-in of fault simulation in EDA tool -Multisim2001 was used to build the DES model for circuits testing, which was proven to be of great help. A brief introduction on NI testing platform, as well as a circuit testing experiment executed with this platform. It's feasibility and advantage was testified in the experiment, illustrating a new way to the automatization of circuit fault diagnosis system.