Test of integrated digital circuits - Design For Testability

The article [E 2 460] entitled "Testing digital integrated circuits – Basics and developments" introduces the main concepts in the field. This article is the second part of a series devoted to the testing of digital integrated circuits, and focuses on the design phase of the integrated circuit, a stage in which it is now essential to take into account its testability in production. Thanks to the use of these design techniques, if a fault occurs during manufacture, it can be detected at the time of testing, and the faulty circuit is then eliminated or repaired.

After defining the criteria for circuit testability, we explore the various architectural techniques that can be integrated during design, whether for simple digital blocks or complex integrated systems. The main standards used in the industry are briefly presented. For more information, the reader can find links to the standards cited in the bibliographic appendix. We also introduce the basic techniques to be used for on-line testing, i.e. testing that takes place while the application is running. Computer-aided design (CAD) software takes circuit testability into account, and its features are described in detail.

We'll see that the proposed techniques introduce additional costs in terms of silicon area and power consumption, and lead to a slight reduction in performance. However, these techniques, and the extra cost they entail, are essential to guarantee the user a minimum level of quality and reliability. Any integrated circuit or system produced today embeds one or more of the solutions mentioned in this article.

A glossary of terms is provided at the end of the article.