Maximum Switching Activity Research Articles

Static Test Compaction for Low-Power Test Sets by Increasing the Switching Activity

This brief describes a static test compaction procedure for low-power test sets, which is based on the observation that a higher switching activity leads to a smaller number of tests. To use this observation in the context of low-power test sets, this brief makes the following new observations. First, considering the number of tests in a given test set where a line $g$ makes a $0 \rightarrow 1$ or a $1 \rightarrow 0$ transition, there are large variations in this number between different lines. Increasing the switching activity only for a subset $G$ of lines that make the smallest numbers of signal transitions is sufficient for achieving test compaction. Second, the switching activity for the subset $G$ can be increased in a way that the specific values that the lines assume can occur during functional operation, and the maximum switching activity for the test set does not increase. These observations allow the compacted test set to remain a low-power test set. Experimental results demonstrate significant reductions in the numbers of tests in low-power test sets for transition faults in benchmark circuits.

Functional Broadside Templates for Low-Power Test Generation

This brief describes a new approach to low-power test generation targeting the maximum switching activity during the fast functional clock cycles of broadside tests. This brief defines functional broadside templates as incompletely-specified broadside tests, which capture the signal-transitions that occur during the fast functional clock cycles of functional broadside tests. The same signal-transitions can occur during functional operation. Therefore, functional broadside templates can guide the generation of low-power test sets when the goal is to match the power dissipation that is possible during functional operation on a line-by-line basis. This brief describes a procedure for computing functional broadside templates from completely-specified functional broadside tests, and a low-power test generation procedure for transition faults based on templates.

A Physical-Location-Aware X-Bit Redistribution for Maximum IR-Drop Reduction

To guarantee that an application-specific integrated circuit (ASIC) meets its timing requirement, at-speed scan testing becomes an indispensable procedure for verifying the performance of ASIC. However, at-speed scan test suffers the test-induced yield loss. Because the switching-activity in test mode is much higher than that in normal mode, the switching-induced large current drawn causes severe IR drop and increases gate delay. X-filling is the most commonly used technique to reduce IR-drop effect during at-speed test. However, the effectiveness of X-filling depends on the number and the characteristic of X-bit distribution. In this paper, we propose a physical-location-aware X-identification which redistributes X-bits so that the maximum switching-activity is guaranteed to be reduced after X-filling. We estimate IR-drop using RedHawk tool and the experimental results on ITC'99 show that our method has an average of 9.42% more reduction of maximum IR-drop as compared to a previous work which redistributes X-bits evenly in all test vectors.

Functional Broadside Tests with Minimum and Maximum Switching Activity

Functional broadside tests were defined as broadside tests that detect target faults using only states that the circuit can visit during functional operation. With functional broadside tests, the peak switching activity and current demands during fast capture cycles can be guaranteed not to exceed those of functional operation, avoiding overtesting due to current demands that cannot be met. Therefore, functional broadside tests make it possible to explore tests with different switching activities as a way to maximize defect detection. For example, a test with a higher switching activity exercises more circuit lines, and is thus likely to activate and detect more defects. In addition, the maximum switching activity under functional broadside tests can be used as an upper bound on the switching activity that can be allowed for other types of tests. Tests with low switching activity may be preferred during wafer testing. Motivated by these applications, we study the range of switching activity possible for the functional broadside tests that detect a target fault, considering transition faults. We use the results to evaluate (low-power) standard broadside test sets.