FAULT MODELING FOR THE TESTING OF MIXED INTEGRATED CIRCUITS

Abstract

The goal of the research described in this paper is to introduce a fault-modeling technique for simulating defective analog components in Mixed Analog/Digital Integrated Circuits. The proposed fault- modeling strategy has been implemented to develop analog fault models representing the effect of spot defects in CMOS circuits. Results from an initial study of opamps are summarized and detailed results from onc example are included as an illustration of the fault- modeling process. 1 Introduction Application of analog components within large digital systems - a typical configuration in modern mixed analog/digital IC's - generates many new challenges in both design and testing areas (l), (2), (3), (4). EspccialIy difficult to solve are testing problems due to the observability limitations caused by the nature of the boundary between the digital and analog components of mixed IC's. Although there are many mixcd IC testing problems, this paper focuses on only one of them - a strategy of fault simulation. More specifically, this paper introduces a fault- modeling methodology which could be applied to capture the malfunctioning of analog components in mixed IC's. The goal of the reported research is to develop fault models that enable efficient simulation of the entire mixed IC by using a technique that is as close as possible to traditional digital circuit simulation techniques. Hence, this paper concentrates solely on the fault- modeling technique. It is organized in the following way. In Section 2, the general fault-modeling methodology developed for analog components of mixed IC's is introduced. In Section 3, an implementation of this methodology for CMOS technology is described in morc detail. Finally, in Section 4, an attempt to generalize obtained results is made in order to determine the practicality of the proposed fault-modeling methodology. This section also gives a list of problems to be solved in the subsequent research dealing with testing of mixcd analog/digital integrated circuits.