Measurement of the Switching Activity of CMOS Digital Circuits at the Gate Level

Accurate estimation of switching activity is very important in digital circuits. In this paper we present a comparison between the evaluation of the switching activity calculated using logic (Verilog) and electrical (HSPICE) simulators. We also study how the variation on the delay model (min, typ, max) and parasitic effects affect the number of transitions in the circuit. Results show a variable and significant overestimation of this measurement using logic simulators even when including postlayout effects. Furthermore, we show the contribution of glitches to the overall switching activity, giving that the treatment of glitches in conventional logic simulators is the main cause of switching activity overestimation.Ministerio de Ciencia y Tecnología TIC 2000-1350Ministerio de Ciencia y Tecnología TIC 2002-228

CUTIE: Beyond PetaOp/s/W Ternary DNN Inference Acceleration with Better-than-Binary Energy Efficiency

We present a 3.1 POp/s/W fully digital hardware accelerator for ternary neural networks. CUTIE, the Completely Unrolled Ternary Inference Engine, focuses on minimizing non-computational energy and switching activity so that dynamic power spent on storing (locally or globally) intermediate results is minimized. This is achieved by 1) a data path architecture completely unrolled in the feature map and filter dimensions to reduce switching activity by favoring silencing over iterative computation and maximizing data re-use, 2) targeting ternary neural networks which, in contrast to binary NNs, allow for sparse weights which reduce switching activity, and 3) introducing an optimized training method for higher sparsity of the filter weights, resulting in a further reduction of the switching activity. Compared with state-of-the-art accelerators, CUTIE achieves greater or equal accuracy while decreasing the overall core inference energy cost by a factor of 4.8x-21x

CAT: A Critical-Area-Targeted Test Set Modification Scheme for Reducing Launch Switching Activity in At-Speed Scan Testing

Reducing excessive launch switching activity (LSA) is now mandatory in at-speed scan testing for avoiding test-induced yield loss, and test set modification is preferable for this purpose. However, previous low-LSA test set modification methods may be ineffective since they are not targeted at reducing launch switching activity in the areas around long sensitized paths, which are spatially and temporally critical for test-induced yield loss. This paper proposes a novel CAT (Critical-Area-Targeted) low-LSA test modification scheme, which uses long sensitized paths to guide launch-safety checking, test relaxation, and X-filling. As a result, launch switching activity is reduced in a pinpoint manner, which is more effective for avoiding test-induced yield loss. Experimental results on industrial circuits demonstrate the advantage of the CAT scheme for reducing launch switching activity in at-speed scan testing.2009 Asian Test Symposium, 23-26 November 2009, Taichung, Taiwa

Optimizing CMOS circuits for low power using transistor reordering

This paper addresses the optimization of a circuit for low power using transistor reordering. The optimization algorithm relies on a stochastic model of a static CMOS gate that includes the power internal nodes of the gate. This power consumption depends on the switching activity and the equilibrium probabilities of the inputs of the gate. The model allows an exploration of the different configurations of a gate that are obtained by recording its transistors. Thus, the best configuration of each gate is selected and the overall power consumption of the circuit is reduced.Peer ReviewedPostprint (published version

Algorithms for Power Aware Testing of Nanometer Digital ICs

At-speed testing of deep-submicron digital very large scale integrated (VLSI) circuits has become mandatory to catch small delay defects. Now, due to continuous shrinking of complementary metal oxide semiconductor (CMOS) transistor feature size, power density grows geometrically with technology scaling. Additionally, power dissipation inside a digital circuit during the testing phase (for test vectors under all fault models (Potluri, 2015)) is several times higher than its power dissipation during the normal functional phase of operation. Due to this, the currents that flow in the power grid during the testing phase, are much higher than what the power grid is designed for (the functional phase of operation). As a result, during at-speed testing, the supply grid experiences unacceptable supply IR-drop, ultimately leading to delay failures during at-speed testing. Since these failures are specific to testing and do not occur during functional phase of operation of the chip, these failures are usually referred to false failures, and they reduce the yield of the chip, which is undesirable. In nanometer regime, process parameter variations has become a major problem. Due to the variation in signalling delays caused by these variations, it is important to perform at-speed testing even for stuck faults, to reduce the test escapes (McCluskey and Tseng, 2000; Vorisek et al., 2004). In this context, the problem of excessive peak power dissipation causing false failures, that was addressed previously in the context of at-speed transition fault testing (Saxena et al., 2003; Devanathan et al., 2007a,b,c), also becomes prominent in the context of at-speed testing of stuck faults (Maxwell et al., 1996; McCluskey and Tseng, 2000; Vorisek et al., 2004; Prabhu and Abraham, 2012; Potluri, 2015; Potluri et al., 2015). It is well known that excessive supply IR-drop during at-speed testing can be kept under control by minimizing switching activity during testing (Saxena et al., 2003). There is a rich collection of techniques proposed in the past for reduction of peak switching activity during at-speed testing of transition/delay faults ii in both combinational and sequential circuits. As far as at-speed testing of stuck faults are concerned, while there were some techniques proposed in the past for combinational circuits (Girard et al., 1998; Dabholkar et al., 1998), there are no techniques concerning the same for sequential circuits. This thesis addresses this open problem. We propose algorithms for minimization of peak switching activity during at-speed testing of stuck faults in sequential digital circuits under the combinational state preservation scan (CSP-scan) architecture (Potluri, 2015; Potluri et al., 2015). First, we show that, under this CSP-scan architecture, when the test set is completely specified, the peak switching activity during testing can be minimized by solving the Bottleneck Traveling Salesman Problem (BTSP). This mapping of peak test switching activity minimization problem to BTSP is novel, and proposed for the first time in the literature. Usually, as circuit size increases, the percentage of don’t cares in the test set increases. As a result, test vector ordering for any arbitrary filling of don’t care bits is insufficient for producing effective reduction in switching activity during testing of large circuits. Since don’t cares dominate the test sets for larger circuits, don’t care filling plays a crucial role in reducing switching activity during testing. Taking this into consideration, we propose an algorithm, XStat, which is capable of performing test vector ordering while preserving don’t care bits in the test vectors, following which, the don’t cares are filled in an intelligent fashion for minimizing input switching activity, which effectively minimizes switching activity inside the circuit (Girard et al., 1998). Through empirical validation on benchmark circuits, we show that XStat minimizes peak switching activity significantly, during testing. Although XStat is a very powerful heuristic for minimizing peak input-switchingactivity, it will not guarantee optimality. To address this issue, we propose an algorithm that uses Dynamic Programming to calculate the lower bound for a given sequence of test vectors, and subsequently uses a greedy strategy for filling don’t cares in this sequence to achieve this lower bound, thereby guaranteeing optimality. This algorithm, which we refer to as DP-fill in this thesis, provides the globally optimal solution for minimizing peak input-switching-activity and also is the best known in the literature for minimizing peak input-switching-activity during testing. The proof of optimality of DP-fill in minimizing peak input-switching-activity is also provided in this thesis

Switching Activity Minimization for XOR Gate Decomposition

In this paper we focus on reduction of switching activity in combinational logic circuits. We are analyzing energy consumption of multi-input XOR gate where changes of inputs occur principally at different times at logic level. We obtain upper and lower bounds for switching activity in various combinations with decomposition of muli-phase input gate. This work presents the algorithm of synthesis for multi-input XOR gate with minimum switching activity. The results presented in this paper are useful for power estimation and low power design. More than 10 to 70 % reduction of in switching activity has been observed using this method.Статья рассматривает вопросы минимизации переключательной активности комбинационных схем. Представлен анализ энергопотребления многовходовых элементов «Исключающее ИЛИ» для случая, когда сигналы на входах меняют свое состояние прин­ципиально в различные моменты времени. Получены формулы, определяющие верх­нюю и нижнюю границы переключательной активности для различных вариантов де­композиции многовходовых элементов. В работе представлен алгоритм синтеза многовходового элемента «Исключающее ИЛИ» с минимальной переключательной активностью. Полученные результаты могут быть использованы для оценки энергопотребления и проектирования с пониженным энергопотреблением. Показано, что применение предложенного подхода позволяет на 10–70 % снизить переключательную активность

Reducing Switching Activity by Test Slice Difference Technique for Test Volume Compression

[[abstract]]This paper presents a test slice difference (TSD) technique to improve test data compression. It is an efficient method and only needs one scan cell. Consequently, hardware overhead is much lower than cyclical scan chains (CSR). As the complexity of VLSI continues to grow, excessive power supply noise has become seriously. We propose a new compression scheme which smooth down the switching activity and reduce the test data volume simultaneously.[[conferencetype]]國際[[conferencelocation]]Taipei, Taiwa

An approach to Measure Transition Density of Binary Sequences for X-filling based Test Pattern Generator in Scan based Design

Switching activity and Transition density computation is an essential stage for dynamic power estimation and testing time reduction. The study of switching activity, transition densities and weighted switching activities of pseudo random binary sequences generated by Linear Feedback shift registers and Feed Forward shift registers plays a crucial role in design approaches of Built-In Self Test, cryptosystems, secure scan designs and other applications. This paper proposed an approach to find transition densities, which plays an important role in choosing of test pattern generator We have analyze conventional and proposed designs using our approache, This work also describes the testing time of benchmark circuits. The outcome of this paper is presented in the form of algorithm, theorems with proofs and analyses table which strongly support the same. The proposed algorithm reduces switching activity and testing time up to 51.56% and 84.61% respectively