Two Timing Samplers

Abstract

Testing VLSl chips presents a variety of problems. some of which can be solved by building on-chip testing structures. On-chip testing structures can allow a designer to test aspects of a circuit which might be difficult to test even with expensive test equipment and moreover can provide reasonable testing hardware to designers who do not have access to sophisticated off-chip testing equipment. In this paper we describe a type of on-chip test structure called H timing sampler which enables the designer to accurately measure when on-chip signal transitions occur. The timing samplers we present are simple. They have been fabricated as part of a multi-project chip and experimental results show that they arc reasonably accurate as well.