In this paper, we propose a parameterized digitally controlled oscillator that can produce oscillating-clock signal with the tunable frequency covering an entire designated range. Moreover, we formulate the all-digital phase-locked loop optimization process as a search problem, during which we can find a good configuration that not only meets the user-defined requirement but also achieves a smaller area and lower power consumption than a typical manual design. The silicon measurement results show that this is indeed a promising new alternative for analog phase-locked loops, especially for advanced nanometer technologies.

For an all-digital phase-locked loop, the frequency range supported is often segmented, and this could cause significant jitter when the operating condition (such as the supply voltage and/or the temperature) changes. To address this issue, we present a scheme, called smooth code-jumping, that can stitch together the segmented frequency profile of a digitally controlled oscillator (DCO) into a continuous range, and thereby reduce the jitter significantly. This scheme incorporates a new mirror-DCO-based calibration scheme to take into account process variations. We validate this scheme by test chips in 0.18-μm CMOS technology. Measurement results show that, when operating at 1 GHz, the rms jitter is 4.3 ps (0.43%UI) and the peak-to-peak jitter is 35.6 ps (3.56%UI), respectively.

Multiphase clock generation (MPCG) is a problem that aims to generate a sequence of clock signals with the same frequency and uniformly shifted phases. In this brief, we present a cell-based MPCG design with two technical merits. We use a process calibration scheme that makes the per-phase delay (defined as the timing difference between two consecutive phases of clock signals) highly accurate. We further exploit a so-called cyclic property to make the achievable per-phase delay much smaller than a buffer delay. A design with 16-phase clock signal (with the per-phase delay of only 100 ps) is used to demonstrate its effectiveness.

Small delay defects escaping traditional delay testing could cause a device to malfunction in the field and thus detecting these defects is often necessary. To address this issue, we propose three test modes in a new methodology called AC-plus scan, in which versatile test clocks can be generated on the chip by embedding an all-digital phase-locked loop (ADPLL) into the circuit under test (CUT). AC-plus scan can be executed on an in-house wireless test platform called HOY system. The first test mode of our AC-plus scan provides a more efficient way to measure the longest path delay associated with each test pattern. Experimental result shows that our method could greatly reduce the test time by 81.8%. The second test mode is designed for volume production test. It could effectively detect small delay defects and provide fast characterization on those defective chips for further processing. This mode could be used to help predict which chips are more likely to fall victim to operational failure in the field. The third test mode is to extract the waveform of each flip-flop's output in a real chip. This is made possible by taking advantage of the almost unlimited test memory our HOY test platform provides, so that we could easily store a great volume of data and reconstruct the waveform for post-silicon debugging. We have successfully fabricated a Viterbi decoder chip with such an AC-plus scan methodology inside to demonstrate its capability.

This work presents a scheme for measuring the timing parameters of a memory's I/O interface - including the setup/hold time and access time. For setup/hold time measurement, we incorporate a procedure that successively adjusts the timing relation between the clock signal and a controllable valid timing window to estimate the setup/hold time. For access time measurement, we propose a circuit that can capture the worst-case access time of an entire Built-In Self-Test (BIST) session as a pulse width, which is then further measured by traditional time-to-digital converter (TDC). Instead of just reporting a digital code, we also propose a calibration scheme so that we can report not just some digital codes, but also their corresponding absolute values. All the design can be constructed by standard cells. We have implemented it in TSMC 0.18nm CMOS process technology. Simulation results show that the setup time error is less than 3%, the hold time error is 7.5%, and the access time error is 4.4%, with about 6.2% area overhead when the memory size is 4096×64.

In modern scan architecture, it is often desirable to compact the output response without jeopardizing the diagnostic resolution. In this paper, we propose an output masking scheme to meet such a stringent requirement. We consider a practical scenario in which an output compactor is in use. We aim to support the harshest condition called compound defect diagnosis, in which faults exist in both the scan chain and the core logic. To overcome the loss of the diagnostic resolution, we incorporate a split-masking scheme, by which one can easily separate the output responses of the faulty chains from those of the fault-free ones. The experimental results demonstrate that the proposed scheme can recover the diagnostic resolution loss induced by an output compactor almost completely without sacrificing the compaction ratio.

In this paper, we present an X-Fill (QC-Fill) method for not only slashing the test time but also reducing the test power (including both capture power and shifting power). QC-Fill, built upon the existing multicasting scan architecture, can coexist with most low-capture-power (LCP) X-fill methods through a multicasting-driven X-Fill method incorporating a clique-stripping scheme. QC-Fill is independent of the ATPG patterns and does not require any area-overhead since it can directly operate on an existing scan architecture incorporating test compression.

This paper presents a layout-based methodology to predict the exact physical location of a bridging defect inside a standard cell. It involves a number of techniques. First of all, most likely intracell bridging defects are identified through layout analysis and then converted into equivalent logic models. Next, we use a new defect-oriented formulation to generate test pattern for each candidate defect so as to further enhance the diagnostic resolution. Experimental results indicate that this methodology can remove 90% false defect candidates beyond gate-level diagnosis for four real designs and ISCAS'85 benchmark circuits.

This paper presents anX-fillscheme that properly utilizes the don't-care bits in test patterns to simultaneously reduce the test time as well as the test power (including both capture power and shifting power). This scheme, called Quick-and-Cool X-fill (QC-Fill), built upon the multicasting-based scan architecture, further leverages on the merits of previous low-capture-power X-fill methods through techniques likemulticasting-driven X-fillandclique stripping.QC-Fillis independent of the automatic test pattern generation patterns and does not require any extra area overhead. Experimental results demonstrate that this scheme strikes a good balance between the seemingly conflicting criteria of low power and test compression.

We introduce in this paper a new scan test methodology that can be programmed to execute in one of two gears - that is, the low-shifting-power scan, and the low-capture-power scan, in one single scan-architecture. This two-gear method provides layered treatment to potential power-induced test failure. First, it attempts to perform scan test in gear 1 without any test time overhead over the traditional scan. Second, in case the failure is caused by excessive capture power, then the test yield loss could be recovered by switching the operation to gear 2, which is a low-capture-power mode, at the cost of extra test time. This methodology is fully compatible with existing DFT tool and requires only small area overhead.

Scan chains are popularly used as the channels for silicon testing and debugging. However, they have also been identified as one of the culprits of silicon failure more recently. To cope with this problem, several scan chain diagnosis approaches have been proposed in the past. The existing methods, however, suffer from one common drawback—that is, they rely on fault models and matching heuristics to locate the faults. Such a paradigm may run into difficulty when the fault under diagnosis does not match the fault model exactly, for example, when there is a bridging between a flip-flop and a logic cell, or the fault is temporal and only manifests itself intermittently. In light of this, we propose in this article a more versatile model-free paradigm for locating the faulty flip-flops in a scan chain, incorporating a number of signal processing techniques, such as filtering and edge detection. These techniques performed on the test responses of the failing chip under diagnosis directly can effectively reveal the fault location(s) in a scan chain. As compared to the previous works, our approach is better capable of handling intermittent faults and bridging faults, even under nonideal conditions, for example, when the core logic is also faulty. Experimental results on several real designs indicate that this approach can indeed catch some nasty faults that previous methods could not catch.