Built-In Self-Test Methodology for A/D Converters

A (partial) Built-in Self-Test (BIST) methodology is proposed for analog to digital (A/D) converters. In this methodology the number of bits of the A/D converter that needs to be monitored externally in a test is reduced. This reduction depends, among other things, on the frequency of the applied test signal. At low test signal frequencies only the least significant bit (LSB) needs to be monitored and a "full" BIST becomes feasible. An analysis is made of the trade-off between the size of the on-chip test circuitry and the accuracy of this BIST techniqu

Built-in-self-test of RF front-end circuitry

Fuelled by the ever increasing demand for wireless products and the advent of deep submicron CMOS, RF ICs have become fairly commonplace in the semiconductor market. This has given rise to a new breed of Systems-On-Chip (SOCs) with RF front-ends tightly integrated along with digital, analog and mixed signal circuitry. However, the reliability of the integrated RF front-end continues to be a matter of significant concern and considerable research. A major challenge to the reliability of RF ICs is the fact that their performance is also severely degraded by wide tolerances in on-chip passives and package parasitics, in addition to process related faults. Due to the absence of contact based testing solutions in embedded RF SOCs (because the very act of probing may affect the performance of the RF circuit), coupled with the presence of very few test access nodes, a Built In Self Test approach (BiST) may prove to be the most efficient test scheme. However due to the associated challenges, a comprehensive and low-overhead BiST methodology for on-chip testing of RF ICs has not yet been reported in literature. In the current work, an approach to RF self-test that has hitherto been unexplored both in literature and in the commercial arena is proposed. A sensitive current monitor has been used to extract variations in the supply current drawn by the circuit-under-test (CUT). These variations are then processed in time and frequency domain to develop signatures. The acquired signatures can then be mapped to specific behavioral anomalies and the locations of these anomalies. The CUT is first excited by simple test inputs that can be generated on-chip. The current monitor extracts the corresponding variations in the supply current of the CUT, thereby creating signatures that map to various performance metrics of the circuit. These signatures can then be post-processed by low overhead on-chip circuitry and converted into an accessible form. To be successful in the RF domain any BIST architecture must be minimally invasive, reliable, offer good fault coverage and present low real estate and power overheads. The current-based self-test approach successfully addresses all these concerns. The technique has been applied to RF Low Noise Amplifiers, Mixers and Voltage Controlled Oscillators. The circuitry and post-processing techniques have also been demonstrated in silicon (using the IBM 0.25 micron RF CMOS process). The entire self-test of the RF front-end can be accomplished with a total test time of approximately 30µs, which is several orders of magnitude better than existing commercial test schemes

A built-in self-test technique for high speed analog-to-digital converters

Fundação para a Ciência e a Tecnologia (FCT) - PhD grant (SFRH/BD/62568/2009

Exploring the Mysteries of System-Level Test

System-level test, or SLT, is an increasingly important process step in today's integrated circuit testing flows. Broadly speaking, SLT aims at executing functional workloads in operational modes. In this paper, we consolidate available knowledge about what SLT is precisely and why it is used despite its considerable costs and complexities. We discuss the types or failures covered by SLT, and outline approaches to quality assessment, test generation and root-cause diagnosis in the context of SLT. Observing that the theoretical understanding for all these questions has not yet reached the level of maturity of the more conventional structural and functional test methods, we outline new and promising directions for methodical developments leveraging on recent findings from software engineering.Comment: 7 pages, 2 figure

Constraint-driven RF test stimulus generation and built-in test

With the explosive growth in wireless applications, the last decade witnessed an ever-increasing test challenge for radio frequency (RF) circuits. While the design community has pushed the envelope far into the future, by expanding CMOS process to be used with high-frequency wireless devices, test methodology has not advanced at the same pace. Consequently, testing such devices has become a major bottleneck in high-volume production, further driven by the growing need for tighter quality control. RF devices undergo testing during the prototype phase and during high-volume manufacturing (HVM). The benchtop test equipment used throughout prototyping is very precise yet specialized for a subset of functionalities. HVM calls for a different kind of test paradigm that emphasizes throughput and sufficiency, during which the projected performance parameters are measured one by one for each device by automated test equipment (ATE) and compared against defined limits called specifications. The set of tests required for each product differs greatly in terms of the equipment required and the time taken to test individual devices. Together with signal integrity, precision, and repeatability concerns, the initial cost of RF ATE is prohibitively high. As more functionality and protocols are integrated into a single RF device, the required number of specifications to be tested also increases, adding to the overall cost of testing, both in terms of the initial and recurring operating costs. In addition to the cost problem, RF testing proposes another challenge when these components are integrated into package-level system solutions. In systems-on-packages (SOP), the test problems resulting from signal integrity, input/output bandwidth (IO), and limited controllability and observability have initiated a paradigm shift in high-speed analog testing, favoring alternative approaches such as built-in tests (BIT) where the test functionality is brought into the package. This scheme can make use of a low-cost external tester connected through a low-bandwidth link in order to perform demanding response evaluations, as well as make use of the analog-to-digital converters and the digital signal processors available in the package to facilitate testing. Although research on analog built-in test has demonstrated hardware solutions for single specifications, the paradigm shift calls for a rather general approach in which a single methodology can be applied across different devices, and multiple specifications can be verified through a single test hardware unit, minimizing the area overhead. Specification-based alternate test methodology provides a suitable and flexible platform for handling the challenges addressed above. In this thesis, a framework that integrates ATE and system constraints into test stimulus generation and test response extraction is presented for the efficient production testing of high-performance RF devices using specification-based alternate tests. The main components of the presented framework are as follows: Constraint-driven RF alternate test stimulus generation: An automated test stimulus generation algorithm for RF devices that are evaluated by a specification-based alternate test solution is developed. The high-level models of the test signal path define constraints in the search space of the optimized test stimulus. These models are generated in enough detail such that they inherently define limitations of the low-cost ATE and the I/O restrictions of the device under test (DUT), yet they are simple enough that the non-linear optimization problem can be solved empirically in a reasonable amount of time. Feature extractors for BIT: A methodology for the built-in testing of RF devices integrated into SOPs is developed using additional hardware components. These hardware components correlate the high-bandwidth test response to low bandwidth signatures while extracting the test-critical features of the DUT. Supervised learning is used to map these extracted features, which otherwise are too complicated to decipher by plain mathematical analysis, into the specifications under test. Defect-based alternate testing of RF circuits: A methodology for the efficient testing of RF devices with low-cost defect-based alternate tests is developed. The signature of the DUT is probabilistically compared with a class of defect-free device signatures to explore possible corners under acceptable levels of process parameter variations. Such a defect filter applies discrimination rules generated by a supervised classifier and eliminates the need for a library of possible catastrophic defects.Ph.D.Committee Chair: Chatterjee, Abhijit; Committee Member: Durgin, Greg; Committee Member: Keezer, David; Committee Member: Milor, Linda; Committee Member: Sitaraman, Sures

Programmable photonics : an opportunity for an accessible large-volume PIC ecosystem

We look at the opportunities presented by the new concepts of generic programmable photonic integrated circuits (PIC) to deploy photonics on a larger scale. Programmable PICs consist of waveguide meshes of tunable couplers and phase shifters that can be reconfigured in software to define diverse functions and arbitrary connectivity between the input and output ports. Off-the-shelf programmable PICs can dramatically shorten the development time and deployment costs of new photonic products, as they bypass the design-fabrication cycle of a custom PIC. These chips, which actually consist of an entire technology stack of photonics, electronics packaging and software, can potentially be manufactured cheaper and in larger volumes than application-specific PICs. We look into the technology requirements of these generic programmable PICs and discuss the economy of scale. Finally, we make a qualitative analysis of the possible application spaces where generic programmable PICs can play an enabling role, especially to companies who do not have an in-depth background in PIC technology