Versatile BIST: An Integrated Approach to On-line/Off-line BIST for Data-Dominated Architectures

Abstract

Built-in Self Test (BIST) is increasingly being used in production testing of VLSICs. In BIST, extra logic is implemented to generate test patterns and compact test responses on chip. However, this extra logic is used only during the test mode. Traditionally, BIST structures used for on-line testing have been different from the BIST structures used for off-line production testing. Replicated hardware, comparators and checkers are typical on-line BIST structures. This is because on-line BIST techniques are mostly based on space or time or information redundancy. On the other hand, typical off-line BIST structures include linear feedback shift register (LFSR) based pattern generators and multiple input signature register (MISR) based test response compactors.

In this paper we report a Versatile BIST approach (VBIST) that targets both off-line and on-line self test. VBIST uses off-line BIST circuitry for on-line testing as well. Unlike traditional on-line self test approaches, VBIST does not use functional data as test inputs. Rather, VBIST generates test patterns and compacts test responses during the normal mode of operation. Furthermore, VBIST coordinates this generation and application of test patterns and compaction of test responses with the usage profile of the modules in the design. VBIST entails little additional impact on performance and area of the design (vis-a-vis the performance and area of a design with off-line BIST). We validated the proposed approach using the Synopsys Behavioral Compiler as the synthesis framework and by writing synthesis scripts for incorporating VBIST constraints.