Sequential Decompressor Network for Scan-Load Switching Noise Reduction
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Solution Overview
Problem
Modern electronic devices face issues with simultaneous switching noise and excessive heat due to high switching activity during test operations, leading to unreliable test responses and increased costs from elongated test times, as existing techniques fail to effectively manage power rail noise and heat dissipation.
Innovation Solution
A method and system utilizing a sequential decompressor network with a linear feedback shift register and a linear spreader network to reduce switching activity during scan shift cycles, employing a nonlinear gating signal to control the clock frequency and data values fed into scan chains, thereby minimizing power supply noise and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high switching activity is used during scan testing, then test coverage and stress testing are improved, but simultaneous switching noise and heat generation increase
Solution Approach 1:
The patent segments the scan chain into multiple groups and applies different clocking strategies to each group. By dividing the large scan chain into smaller segments that are clocked at different times, the simultaneous switching noise is reduced while maintaining comprehensive test coverage through systematic exhaustion of all possible test patterns.
Solution Approach 2:
The patent implements periodic clocking where scan chains are clocked in alternating phases. The first scan chain is clocked for a predetermined number of cycles, then the second scan chain is clocked for the same number of cycles, creating a periodic action that distributes switching activity over time and reduces simultaneous switching noise while maintaining test effectiveness.
2Reliability
If high switching activity is used during scan testing, then test stress and coverage are improved, but heat generation increases
Solution Approach 1:
The patent divides the scan chain into multiple groups that are clocked separately. This segmentation allows test patterns to be applied with reduced switching activity in each segment, lowering overall heat generation while maintaining comprehensive test coverage and stress testing capability through systematic pattern exhaustion.
Solution Approach 2:
The patent uses periodic clocking where different scan chains are activated in alternating phases. This periodic action distributes the switching activity over extended time periods, reducing the peak heat generation rate while still achieving sufficient test stress and coverage through repeated cycling of test patterns.
3Temperature
If operational speed is reduced to manage heat, then heat dissipation is improved, but test time increases
Solution Approach 1:
The patent segments the testing process into multiple phases where different scan chains are tested in alternation. This allows the system to maintain higher overall testing throughput by working on multiple chains simultaneously at different times, reducing total test time while managing heat through controlled switching activity in each segment.
Solution Approach 2:
The patent implements periodic testing cycles where scan chains are tested in alternating phases. This periodic action enables the system to maintain high testing productivity by continuously working on different chains without requiring all chains to be tested simultaneously, thus reducing total test time while managing thermal loads through time-distributed switching activity.
4Device complexity
If conventional decompression techniques are used, then test pattern generation is simplified, but power rail noise and switching activity increase
Solution Approach 1:
The patent segments the decompression process by dividing the scan chain into multiple groups that are clocked separately. This segmentation allows simpler decompression logic to be applied to each segment individually, reducing the overall complexity while simultaneously lowering power rail noise through distributed switching activity across time and space.
Solution Approach 2:
The patent uses periodic clocking of different scan chains in alternating phases to simplify the decompression process. This periodic action allows standard decompression techniques to be applied to each chain in turn, maintaining algorithmic simplicity while reducing power rail noise through time-distributed switching that prevents simultaneous noise generation across all chains.
Data Source
AI summary
A method and system for reducing switching activity of a spreader network during a scan-load operation is disclosed. According to one embodiment, a spreader network receives a plurality of scan input signals from a tester. A linear feedback shift register of the spread network is updated using the plurality of scan input signals. Each bit of the linear feedback shift register is shifted at each shift cycle for a plurality of shift cycles. The linear feedback shift register outputs a nonlinear gating signal using a first set of outputs and a data value feeding one or more scan chains of the spreader network using a second set of outputs. The pipeline clock of a pipeline element of the scan chains is gated using the nonlinear gating signal, and the data value is fed to the scan chains based on the pipeline clock. The scan chains are fed with updated values at the pipeline stage.