At-speed scan testing may suffer from severe yield loss due to the launch safety problem, where test responses are invalidated by excessive launch switching activity (LSA) caused by test stimulus launching in the at-speed test cycle. However, previous low-power test generation techniques can only reduce LSA to some extent but cannot guarantee launch safety. This paper proposes a novel & practical power-aware test generation flow, featuring guaranteed launch safety. The basic idea is to enhance ATPG with a unique two-phase (rescue & mask) scheme by targeting at the real cause of the launch safety problem, i.e., the excessive LSA in the neighboring areas (namely impact areas) around long paths sensitized by a test vector. The rescue phase is to reduce excessive LSA in impact areas in a focused manner, and the mask phase is to exclude from use in fault detection the uncertain test response at the endpoint of any long sensitized path that still has excessive LSA in its impact area even after the rescue phase is executed. This scheme is the first of its kind for achieving guaranteed launch safety with minimal impact on test quality and test costs, which is the ultimate goal of power-aware at-speed scan test generation.

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Power-aware test generation with guaranteed launch safety for at-speed scan testing

During an at-speed scan-based test, excessive capture power may cause significant current demand, resulting in the IR-drop problem and unnecessary yield loss. Many methods address this problem by reducing the switching activities of power-risky patterns. These methods may not be efficient when the number of power-risky patterns is large or when some of the patterns require extremely high power. In this paper, we propose discarding all power-risky patterns and starting with power-safe patterns only. Our test generation procedure includes two processes, namely, test pattern refinement and low-power test pattern regeneration. The first process is used to refine the power-safe patterns to detect faults originally detected only by power-risky patterns. If some faults are still undetected after this process, the second process is applied to generate new power-safe patterns to detect these faults. The patterns obtained using the proposed procedure are guaranteed to be power-safe for the given power constraints. To the best of our knowledge, this is the first method that refines only the power-safe patterns to address the capture power problem. Experimental results on ISCAS'89 and ITC'99 benchmark circuits show that an average of 75% of faults originally detected only by power-risky patterns can be detected by refining power-safe patterns and that most of the remaining faults can be detected by the low-power test generation process. Furthermore, the required test data volume can be reduced by 12.76% on average with little or no fault coverage loss.

Capture-Power-Safe Test Pattern Determination for At-Speed Scan-Based Testing

In return for increased operating frequency and reduced supply voltage in nano-scale designs, their vulnerability to IR-drop-induced yield loss grew increasingly apparent. Therefore, it is necessary to consider delay increase effect due to IR-drop during at-speed scan testing. However, it consumes significant amounts of time for precise IR-drop analysis. This paper addresses this issue with a novel per-cell dynamic IR-drop estimation method. Instead of performing time-consuming IR-drop analysis for each pattern one by one, the proposed method uses global cycle average power profile for each pattern and dynamic IR-drop profiles for a few representative patterns, thus total computation time is effectively reduced. Experimental results on benchmark circuits demonstrate that the proposed method achieves both high accuracy and high time-efficiency.

A fast and accurate per-cell dynamic IR-drop estimation method for at-speed scan test pattern validation

The efficiency of biogas production during anaerobic digestion depends heavily on optimal dosing ratios and stable operations which can not be achieved without accurate and reliable monitoring and control of the dry matter (DM) and organic dry matter (oDM) content. The materials in biogas processes to be measured are either stored in a vessel flowing in a pipe, either as a liquid or as solid particles in pneumatic or liquid assisted transportation with a wide area of the content of DM (1% 90). In such cases microwave sensors provide an attractive solution, because microwaves penetrate most materials allowing the non destructive measurement to be representative for a special volume or the cross section of the pipe. The setup of the measuring system for materials with high water content and first results are presented.

Continuous process monitoring for biogas plants using microwave sensors

This paper proposes a novel scheme to manage capture power in a pinpoint manner for achieving guaranteed capture power safety, improved small-delay test capability, and minimal test cost impact in at-speed scan test generation. First, switching activity around each long path sensitized by a test vector is checked to characterize it as hot (with excessively-high switching activity), warm (with normal/functional switching activity), or cold (with excessively-low switching activity). Then, X-restoration/X-filling-based rescue is conducted on the test vector to reduce switching activity around hot paths. If the rescue is insufficient to turn a hot path into a warm path, mask is then conducted on expected test response data to instruct the tester to ignore the potentially-false test response value from the hot path, thus achieving guaranteed capture power safety. Finally, X-restoration/X-filling-based warm-up is conducted on the test vector to increase switching activity around cold paths for improving their small-delay test capability. This novel approach of pinpoint capture power management has significant advantages over the conventionalapproachofglobalcapturepower management, as demonstrated by evaluation results on large ITC'99 benchmark circuits and detailed path delay analysis.

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On pinpoint capture power management in at-speed scan test generation

Capture-safety, defined as the avoidance of any timing error due to unduly high launch switching activity in capture mode during at-speed scan testing, is critical for avoiding test- induced yield loss. Although point techniques are available for reducing capture IR-drop, there is a lack of complete capture-safe test generation flows. The paper addresses this problem by proposing a novel and practical capture-safe test generation scheme, featuring (1) reliable capture-safety checking and (2) effective capture-safety improvement by combining X-bit identification & X-filling with low launch- switching-activity test generation. This scheme is compatible with existing ATPG flows, and achieves capture-safety with no changes in the circuit-under-test or the clocking scheme.

A Capture-Safe Test Generation Scheme for At-Speed Scan Testing

Test data modification based on test relaxation and X-filling is the preferable approach for reducing excessive IR-drop in at-speed scan testing to avoid test-induced yield loss. However, none of the existing test relaxation methods can control the distribution of identified donpsilat care bits (X-bits), thus adversely affecting the effectiveness of IR-drop reduction. In this paper, we propose a novel test relaxation method, called Distribution-Controlling X-Identification (DC-XID), which controls the distribution of X-bits identified from a set of fully-specified test vectors for the purpose of effectively reducing IR-drop. Experimental results on large industrial circuits demonstrate the effectiveness and practicality of the proposed method in reducing IR-drop, without any impact on fault coverage, test data volume, or test circuit size.

/pdf/effective-ir-drop-reduction-in-at-speed-scan-testing-using-zlttcsy2ab.pdf

Effective IR-drop reduction in at-speed scan testing using Distribution-Controlling X-Identification

Reducing IR-drop in the test cycle during at-speed scan testing has become mandatory for avoiding test-induced yield loss. An efficient approach for this purpose is post-ATPG test modification based on X-identification and X-filling since it causes no circuit/clock design change and no test vector count inflation. However, applying this approach to test compression has been considered challenging due to the limited availability of X-bits. This paper solves this serious problem by proposing a novel and practical CA (Compression-Aware) test modification scheme for reducing IR-drop in the widely-used broadcast-scan based test compression environment. This unique scheme features (1) CA circuit remodeling for minimizing the effort of applying test modification to broadcast-scan-based test compression, (2) CA X-identification for increasing X-bits for risky test vectors, and (3) CA X-filling for effectively using limited X-bits in reducing IR-drop. As a result, the CA test modification scheme can achieve significant IR-drop reduction even when a test cube only has a small number of X-bits. This advantage is clearly demonstrated by experimental results on three compression configurations created from an industrial circuit.

A novel post-ATPG IR-drop reduction scheme for at-speed scan testing in broadcast-scan-based test compression environment

Issues on power consumption and IR-drop in testing become serious problems. Some troubles, such as tester fails due to too much power consumption or IR-drop, test escapes due to slowed clock cycle, and so on, can happen in test floors. In this paper, we propose a power and noise aware scan test method. In the method, power-aware DFT and power-aware ATPG are executed based on the preliminary power/noise estimation for test. Experimental results illustrate the effect of reducing IR-drop for both shift and capture mode in scan test.

Power and noise aware test using preliminary estimation

PROBLEM TO BE SOLVED: To obtain a state inside a residence by deciding the state from sensing information of a variety of terminal devices including a residential alarm unit installed in the residence and by reporting it to the outside through a network. SOLUTION: A decision processing unit 50 in a home controller 10 outputs a decision result from a notification unit 30 by deciding an electronic message received from a terminal device such as a human sensor 12, so as to report it from a network adapter 34 to an external terminal device 22 through the Internet 20. The decision processing unit 50 includes a function of a safety confirmation unit 52 for transmitting a safety confirmation mail to the external terminal device 22 on receiving the human detection message from the human sensor 12. COPYRIGHT: (C)2010,JPO&INPIT

Kenji Noda

Papers

A Capture-Safe Test Generation Scheme for At-Speed Scan Testing

Effective IR-drop reduction in at-speed scan testing using Distribution-Controlling X-Identification

A novel post-ATPG IR-drop reduction scheme for at-speed scan testing in broadcast-scan-based test compression environment

Power and noise aware test using preliminary estimation

Residential control apparatus and residential alarm unit