Filter Circuit for Compacted Test Response Error Detection
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Solution Overview
Problem
Current test response compaction schemes struggle to efficiently handle unknown states in integrated circuit testing, leading to corrupted test signatures and increased test costs due to the need for additional output pins and complex error detection methods.
Innovation Solution
A method and apparatus that filter compacted test responses to remove the effects of unknown values, using a programmable network of combinational logic to logically combine test response values and control signals, allowing for error detection without increasing output pins or requiring special ATE support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If test response compaction is used to reduce test data volume, then test costs are reduced, but unknown states in test responses corrupt test signatures and reduce measurement precision
Solution Approach 1:
The patent extracts and removes unknown values from compacted test responses using a filter circuit. The filter identifies and eliminates the contribution of unknown values to the compacted response, allowing the remaining valid test signature information to be accurately compared against expected values for fault detection.
Solution Approach 2:
The patent introduces a filter circuit as an intermediary component between the compactor and the comparison logic. This filter acts as a mediator that processes the compacted test response by removing unknown value effects before the signature comparison is performed, thus protecting the measurement precision without affecting the compaction ratio.
2Reliability
If additional output pins are used to detect errors in the presence of unknown values, then error detection capability is improved, but device complexity and test costs increase
Solution Approach 1:
The patent makes the existing compacted test response output multi-functional by using a filter circuit that processes the same output to remove unknown value effects. This allows the single compacted response to serve both as a compressed data representation and as an error-detectable signal without requiring additional dedicated output pins for error detection.
3Reliability
If complex error detection methods are used to handle unknown values, then error detection capability is improved, but device complexity and test costs increase
Solution Approach 1:
The patent introduces a filter circuit as an intermediary component between the compactor and the comparison logic. This filter acts as a mediator that processes the compacted test response by removing unknown value effects before the signature comparison is performed, thus protecting the measurement precision without requiring additional dedicated output pins for error detection.
Data Source
AI summary
Methods, apparatus, and systems for filtering compacted test responses are disclosed. The methods, apparatus, and systems can be used, for example, to remove the effects of unknown test values. For instance, in one embodiment, a compacted test response from a compactor of a circuit-under-test is received. In this embodiment, the compacted test response includes one or more compacted test response values that are dependent on one or more respective unknown values. The compacted test response is filtered to remove the dependency of at least some of the compacted test response values on the one or more respective unknown values, and a filtered test response is output. Various filtering circuits and testing systems are also disclosed.