V. R. Devanathan

Bio: V. R. Devanathan is an academic researcher from Texas Instruments. The author has contributed to research in topics: Automatic test pattern generation & Benchmark (computing). The author has an hindex of 9, co-authored 33 publications receiving 261 citations. Previous affiliations of V. R. Devanathan include Indian Institute of Technology Madras.

Glitch-Aware Pattern Generation and Optimization Framework for Power-Safe Scan Test

Abstract: Excessive dynamic voltage drop in the power supply rails during test mode is known to result in false failures and impact yield when testing devices that use low-cost wire-bond packages. Identifying and debugging such test failures is a complex and effort-intensive process, especially when scan compression is involved. From a design cycle-tune view point, it is best to avoid this problem by generating "power-safe" scan patterns. The generation of power-safe patterns must take into consideration the DFT architecture, physical design, tuning and power constraints. In this paper, the authors propose such a framework and show experimental results on some benchmark circuits. The framework can address a non-uniform power grid and region-based power constraints. The authors show that glitching activity on nodes must be considered in order to correctly handle constraints on instantaneous peak power. The framework includes a power profiler that can analyze a pattern source for violations and a PODEM-based pattern generation engine for generating power-safe patterns.

PMScan : A power-managed scan for simultaneous reduction of dynamic and leakage power during scan test

Abstract: In sub-70 nm technologies, leakage power becomes a significant component of the total power. Designers address this concern by extensive use of adaptive voltage scaling techniques to reduce dynamic as well as leakage power. Low-power scan test schemes that have evolved in the past primarily address dynamic power reduction, and are less effective in reducing the total power. We propose a power-managed scan (PMScan) scheme which exploits the presence of adaptive voltage scaling logic to reduce test power. We also discuss some practical implementation challenges that arise when the proposed scheme is employed on industrial designs. Experimental results on benchmark circuits and industrial designs show a significant reduction in dynamic and leakage power. The proposed method can also be used as a vehicle to trade-off test application time with test power by suitably adjusting the scan shift frequency and scan-mode power supplies.

A stochastic pattern generation and optimization framework for variation-tolerant, power-safe scan test

Abstract: Process variation is an increasingly dominant phenomenon affecting both power and performance in sub-100 nm technologies Cost considerations often do not permit over-designing the power supply infrastructure for test mode, considering the worst-case scenario Test application must not over-exercise the power supply grids, lest the tests will damage the device or lead to false test failures The problem of debugging a delay test failure can therefore be highly complex We argue that false delay test failures can be avoided by generating "safe" patterns that are tolerant to on-chip variations A statistical framework for power-safe pattern generation is proposed, which uses process variation information, power grid topology and regional constraints on switching activity Experimental results are provided on benchmark circuits to demonstrate the effectiveness of the framework

Interactive presentation: On power-profiling and pattern generation for power-safe scan tests

Abstract: With increasing use of low cost wire-bond packages for mobile devices, excessive dynamic IR-drop may cause tests to fail on the tester. Identifying and debugging such scan test failures is a very complex and effort-intensive process. A better solution is to generate correct-by-construction "power-safe" patterns. Moreover, with glitch power contributing to a significant component of dynamic power, pattern generation needs to be timing-aware to minimize glitching. In this paper, we propose a timing-based, power and layout-aware pattern generation technique that minimizes both global and localized switching activity. Techniques are also proposed for power-profiling and optimizing an initial pattern set to obtain a power-safe pattern set, with the addition of minimal patterns. The proposed technique also comprehends irregular power grid topologies for constraints on localized switching activity. Experiments on ISCAS benchmark circuits reveal the effectiveness of the proposed scheme.

Methodology for low power test pattern generation using activity threshold control logic

Abstract: This paper proposes a new technique of power-aware test pattern generation, wherein the test mode power constraints are specified using pseudo hardware logic functions (referred to as power constraint circuits) that augment the target circuit fed to the ATPG tool. The novelty of this approach is three-fold: (i) The ATPG tool only sees the enhanced circuit. This influences the generation of the test cubes themselves, as against post-processing of these cubes for a given pattern. (ii) Pattern generation can be driven to minimize test power according to a programmable switching activity threshold, and hence, is scalable. (iii) The same constraint circuit can also be effectively used for pattern filtering to isolate patterns which cause high switching activity. Additionally, the proposed method does not require any changes to the pattern generation tool or process. This paper describes the methodology, together with techniques for realizing the hardware circuit and specifying thresholds. Experimental results on various benchmark circuits (including an industrial design) are presented to show the effectiveness of this approach.

Power-aware test: Challenges and solutions

Abstract: Power-aware test is increasingly becoming a major manufacturing test consideration due to the problems of increased power dissipation in various test modes as well as test implications that arise due to the usage of various low-power design technologies in devices today. Several challenges emerge for test engineers and test tool developers, including (and not restricted to) understanding of various concerns associated with power-aware test, development of power-aware design-for-test (DFT), automatic test pattern generation (ATPG) techniques, and test power analysis flows, evaluation of their efficacy and ensuring easy/rapid deployment. This paper highlights concerns and challenges in power-aware test, surveys various practices drawn from both academia and industry, and points out critical gaps that need to be addressed in the future.

Reducing Power Supply Noise in Linear-Decompressor-Based Test Data Compression Environment for At-Speed Scan Testing

Abstract: Yield loss caused by excessive power supply noise has become a serious problem in at-speed scan testing. Although X-filling techniques are available to reduce the launch cycle switching activity, their performance may not be satisfactory in the linear-decompressor-based test compression environment. This work is the first to solve this problem by proposing a novel integrated ATPG scheme that efficiently and effectively performs compressible X-filling. Related theoretical principles are established, based on which the problem size is substantially reduced. The proposed scheme is validated by large benchmark circuits as well as an industry design in the embedded deterministic test (EDT) environment.

Power management events profiling

Abstract: In a method for monitoring power consumption by a system within an integrated circuit, one or more software programs are executed on the system on a chip (SOC). While the program executes, power control settings of a plurality of functional units within the SOC may be adjusted in response to executing the one or more software programs, whereby power consumption within the SOC varies over time. The power control settings may be changed in response to explicit directions from the executing software, or may occur autonomously in response to load monitoring control modules within the SOC. A sequence of power states is reported for the plurality of functional units within the SOC. Each of the sequence of power states may include clock frequencies from multiple clock domains, voltage levels for multiple voltage domains, initiator activity, target activity, memory module power enablement, or power enablement of each of the plurality of functional units.

CTX: A Clock-Gating-Based Test Relaxation and X-Filling Scheme for Reducing Yield Loss Risk in At-Speed Scan Testing

Abstract: At-speed scan testing is susceptible to yield loss risk due to power supply noise caused by excessive launch switching activity. This paper proposes a novel two-stage scheme, namely CTX (Clock-Gating-Based Test Relaxation and X-Filling), for reducing switching activity when test stimulus is launched. Test relaxation and X-filling are conducted (1) to make as many FFs inactive as possible by disabling corresponding clock-control signals of clock-gating circuitry in Stage-1 (Clock-Disabling), and (2) to make as many remaining active FFs as possible to have equal input and output values in Stage-2 (FF-Silencing). CTX effectively reduces launch switching activity, thus yield loss risk, even with a small number of donpsilat care (X) bits as in test compression, without any impact on test data volume, fault coverage, performance, and circuit design.

Test strategies for low power devices

Abstract: Ultra low-power devices are being developed for embedded applications in bio-medical electronics, wireless sensor networks, environment monitoring and protection, etc. The testing of these low-cost, low-power devices is a daunting task. Depending on the target application, there are stringent guidelines on the number of defective parts per million shipped devices. At the same time, since such devices are cost-sensitive, test cost is a major consideration. Since system-level power-management techniques are employed in these devices, test generation must be power- management-aware to avoid stressing the power distribution infrastructure in the test mode. Structural test techniques such as scan test, with or without compression, can result in excessive heat dissipation during testing and damage the package. False failures may result due to the electrical and thermal stressing of the device in the test mode of operation, leading to yield loss. This paper considers different aspects of testing low-power devices and some new techniques to address these problems.