An ADC BIST with on-chip ramp generator

This work presents built-in self-test (BIST) techniques for the production testing of mixed signal circuits. The special test strategy for the typical mixed-signal component analog-to-digital converter (ADC) is discussed. The traditional test for such mixed-signal components can be completed through a DSP-based mixed-signal tester with an arbitrary waveform generator and a signal digitizer, but such a test is very costly and time consuming. Hence, a BIST strategy based on an on chip ramp generator (OCRG) is proposed in this work for testing ADC. This BIST method has an advantage testing ADC without DAC to overcome area overhead. This BIST method realizes the test controller, test pattern generation and output response analyser at the aspect of the on-chip circuitry. The demonstration of the proposed BIST is given through various simulation results in the last parts of this work.     

Scalable Delay Fault BIST for Use with Low-Cost ATE

We present a BIST architecture based on a Multi-Input Signature Register (MISR) expanding single input vectors into sequences, which are used for testing of delay faults. Input vectors can be stored on-chip or in the ATE; in the latter case, a low speed tester can be employed though the sequences are applied at-speed to the block-under-test. The number of input vectors (and thus the area demand on-chip or ATE memory requirements) can be traded for the test application time.We propose several methods for generating input vectors, which differ in test application time, area requirements and algorithm run-time. As all of them require only a two-pattern test as input, IP cores can be handled by these methods.The block-under-test can be switched off for some amount of time between application of consecutive input vectors. We provide arguments why this approach may be the only way to meet thermal and power constraints. Furthermore, we demonstrate how the BIST scheme can use these cool-down breaks for re-configuration.     

SoC嵌入式flash存储器的内建自测试设计

深亚微米技术背景下，嵌入式存储器在片上系统芯片(system-on-a-chip，SoC)中占有越来越多的芯片面积．嵌入式存储器的测试正面临诸多新的挑战。本文论述了两种适合SoC芯片中嵌入式flash存储器的内建自测试设计方案。详细讨论了专用硬件方式内建自测试的设计及其实现，并且提出了一种新型的软硬协同方式的内建自测试设计。这种新型的测试方案目标在于结合专用硬件方式内建自测试方案并有效利用SoC芯片上现有的资源，以保证满足测试过程中的功耗限制，同时在测试时间和芯片面积占用及性能之间寻求平衡。最后对两种方案的优缺点进行了分析对比。     

Deterministic Built-in Pattern Generation for Sequential Circuits

We present a new pattern generation approach for deterministic built-in self testing (BIST) of sequential circuits. Our approach is based on precomputed test sequences, and is especially suited to sequential circuits that contain a large number of flip-flops but relatively few controllable primary inputs. Such circuits, often encountered as embedded cores and as filters for digital signal processing, are difficult to test and require long test sequences. We show that statistical encoding of precomputed test sequences can be combined with low-cost pattern decoding to provide deterministic BIST with practical levels of overhead. Optimal Huffman codes and near-optimal Comma codes are especially useful for test set encoding. This approach exploits recent advances in automatic test pattern generation for sequential circuits and, unlike other BIST schemes, does not require access to a gate-level model of the circuit under test. It can be easily automated and integrated with design automation tools. Experimental results for the ISCAS 89 benchmark circuits show that the proposed method provides higher fault coverage than pseudorandom testing with shorter test application time and low to moderate hardware overhead.     

Test-Per-Clock Logic BIST with Semi-Deterministic Test Patterns and Zero-Aliasing Compactor

We present a test-per-clock BIST scheme using memory for storing test patterns that reduces the number of clock cycle necessary for testing. Thus, the test application time is shorter and energy consumption is lower than those in other solutions. The test hardware consists of a space compactor and a MISR, which provides zero error aliasing for modeled faults. The test pattern generator (TPG) scheme is based on a T-type flip-flop feedback shift register. The generator can be seeded similarly to a D-type flip-flop shift register. It generates test patterns in a test-per-clock mode. The TPG pattern sequence is modified at regular intervals by adding a modulo-2 bit from a modification sequence, which is stored in a memory. The memory can be either a ROM on the chip or a memory in the tester. The test patterns have both random and deterministic properties, which are advantageous for the final quality of the resulting test sequence. The number of bits stored in the memory, number of clock cycles, hardware overhead and the parameters of the resulting zero aliasing space compactor and MISR are given for the ISCAS benchmark circuits. The experiments demonstrate that the BIST scheme provides shorter test sequences than other methods while the hardware overhead and memory requirements are kept low.     

Two-Dimensional Test Data Compression for Scan-Based Deterministic BIST

In this paper a novel architecture for scan-based mixed mode BIST is presented. To reduce the storage requirements for the deterministic patterns it relies on a two-dimensional compression scheme, which combines the advantages of known vertical and horizontal compression techniques. To reduce both the number of patterns to be stored and the number of bits to be stored for each pattern, deterministic test cubes are encoded as seeds of an LFSR (horizontal compression), and the seeds are again compressed into seeds of a folding counter sequence (vertical compression). The proposed BIST architecture is fully compatible with standard scan design, simple and flexible, so that sharing between several logic cores is possible. Experimental results show that the proposed scheme requires less test data storage than previously published approaches providing the same flexibility and scan compatibility.     

A low-cost digital frequency testing approach for mixed-signal devices using ΣΔ modulation

This paper presents a digital approach to frequency testing of Analogue and mixed-signal (AMS) circuits. This approach is aimed at facilitating low-cost test techniques for system-on-chip (SoC) devices, rendering the test of mixed-signal cores compatible with the use of a low-cost digital tester. Analogue test signal generation is performed on-chip by low pass filtering a sigma–delta (ΣΔ) encoded bit-stream. Analogue harmonic test response analysis is also performed on-chip using square wave modulation and ΣΔ modulation. Since both analogue signal generation and test response analysis are digitally programmable on-chip, compatibility with a low-cost digital tester is ensured. Optimisation of test signatures is discussed in detail as a trade-off between fault and yield coverage. A 0.18 μm CMOS implementation of this BIST technique is presented, including some experimental results.     

Diagnosing At-Speed Scan BIST Circuits Using a Low Speed and Low Memory Tester

Numerous solutions have been proposed to reduce test data volume and test application time during manufacturing testing of digital devices. However, time to market challenge also requires a very efficient debug phase. Error identification in the test responses can become impractically slow in the debug phase due to large debug data, slow tester speed, and limited memory of the tester. In this paper, we investigate the problems and solutions related to using a relatively slow and limited memory tester to observe the at-speed behavior of fast circuits. Our method can identify all errors in at-speed scan BIST environment without any aliasing and using only little extra overhead by way of a multiplexer and masking circuit for diagnosis. Our solution takes into account the relatively slower speed of the tester and the reload time of the expected data to the tester memory due to limited tester memory while reducing the test/debug cost. Experimental results show that the test application time by our method can be reduced by a factor of 10 with very little hardware overhead to achieve such advantage.     

Testing and Reliability Techniques for High-Bandwidth Embedded RAMs

Application-specific integrated circuits (ASICs) and high-performance processors such as Itanium and Compaq Alpha use a total of almost 75% of chip real estate for accommodating various types of embedded (or on-chip) memories. Although most of these embedded memories are single-port static (and in relatively few cases, dynamic) RAMs today, the high demand for bandwidth in digital television, fast signal processing, and high-speed networking applications will also fuel the need for on-chip multiport memories in the foreseeable future. The reliability of a complex VLSI chip will depend largely on the reliability of these embedded memory blocks. With device dimensions moving rapidly toward the ultimate physical limits of device scaling, which is in the regime of feature sizes of 50 nm or so, a host of complex failure modes is expected to occur in memory circuits. This tutorial underlines the need for appropriate testing and reliability techniques for the present to the next generation of embedded RAMs. Topics covered include: reliability and quality testing, fault modeling, advanced built-in self-test (BIST), built-in self-diagnosis (BISD), and built-in self-repair (BISR) techniques for high-bandwidth embedded RAMs.     

Built-in Self Test Based on Multiple On-Chip Signature Checking

We propose an improved BIST architecture which supports on-chip comparison of signatures at no significant increase in area. The proposed test architecture reduces detection latency and eliminates the lengthy scan-out phase from each test session by allowing testing and on-chip signature comparison of multiple intermediate signatures to occur concurrently. The work is based on a novel procedure to implement the multiple on-chip signature checking. We show that such a test method gives significant improvements in test application time and aliasing probability. This paper also presented two techniques to minimize the test area overhead with a very small test time overhead compare to the conventional schemes. These techniques resulted in up to 80% savings in test area overhead for some High-level synthesis benchmark circuits. This paper also presents an aliasing analysis of the proposed scheme.     

A Built-in Self-Test Scheme for Memory Interfaces Timing Test and Measurement

This paper presents a Built-In Self-Test (BIST) technique to test the setup and hold times of memory interface circuitry. The BIST scheme generates data and clock using an on-chip pattern generator. The relative timing difference between data and clock is controlled using a cycle-by-cycle control method for testing. Two test methods of static and dynamic modes have been presented to measure the timing difference and then are used to specify the setup and hold times. The static mode is mainly used to detect pass or fail for timing specifications, and the dynamic mode is devised to measure the amount of timing mismatches and thus detect timing margin degradations due to the timing delay mismatches. Using these two test modes, the BIST scheme obtains test results with low frequency signals, which are compatible with low performance testers. The test chip including the BIST scheme has been fabricated with a commercial 0.18-μm CMOS process. The chip measurement results are shown to validate the testability of the BIST scheme for the setup and hold times of memory devices.     

Application of Deterministic Logic BIST on Industrial Circuits

We present the application of a deterministic logic BIST scheme based on bit-flipping on state-of-the-art industrial circuits. Experimental results show that complete fault coverage can be achieved for industrial circuits up to 100 K gates with 10,000 test patterns, at a total area cost for BIST hardware of typically 5–15%. It is demonstrated that a trade-off is possible between test quality, test time, and silicon area. In contrast to BIST schemes based on test point insertion no modifications of the circuit under test are required, complete fault efficiency is guaranteed, and the impact on the design process is minimized.     

Deterministic Test Vector Compression/Decompression for Systems-on-a-Chip Using an Embedded Processor

A novel approach for using an embedded processor to aid in deterministic testing of the other components of a system-on-a-chip (SOC) is presented. The tester loads a program along with compressed test data into the processor's on-chip memory. The processor executes the program which decompresses the test data and applies it to scan chains in the other components of the SOC to test them. The program itself is very simple and compact, and the decompression is done very rapidly, hence this approach reduces both the amount of data that must be stored on the tester and reduces the test time. Moreover, it enables at-speed scan shifting even with a slow tester (i.e., a tester whose maximum clock rate is slower than the SOC's normal operating clock rate). A procedure is described for converting a set of test cubes (i.e., test vectors where the unspecified inputs are left as X's) into a compressed form. A program that can be run on an embedded processor is then given for decompressing the test cubes and applying them to scan chains on the chip. Experimental results indicate a significant amount of compression can be achieved resulting in less data that must be stored on the tester (i.e., smaller tester memory requirement) and less time to transfer the test data from the tester to the chip.     

A Scan-BIST Structure to Test Delay Faults in Sequential Circuits

Delay testing that requires the application of consecutive two-pattern tests is not an easy task in a scan-based environment. This paper proposes a novel approach to the delay fault testing problem in scan-based sequential circuits. This solution is based on the combination of a BIST structure with a scan-based design to apply delay test pairs to the circuit under test.     

Mixed-Mode BIST Using Embedded Processors

In complex systems, embedded processors may be used to run software routines for test pattern generation and response evaluation. For system components which are not completely random pattern testable, the test programs have to generate deterministic patterns after random testing. Usually the random test part of the program requires long run times whereas the part for deterministic testing has high memory requirements.In this paper it is shown that an appropriate selection of the random pattern test method can significantly reduce the memory requirements of the deterministic part. A new, highly efficient scheme for software-based random pattern testing is proposed, and it is shown how to extend the scheme for deterministic test pattern generation. The entire test scheme may also be used for implementing a scan based BIST in hardware.     

Partial Reset Methodology and Experiments for Improving Random-Pattern Testability and BIST of Sequential Circuits

Partial reset has been shown to have significant impact on test generation for sequential circuits in a stored-pattern test application environment. In this paper, we explore the use of partial reset in fault-independent testing and built-in self-test (BIST) of non-scan sequential circuits. We select a subset of flip-flops in the circuit to be resetable to logic one or zero during the application of the test vectors. The resetting is performed with random frequency. The selection of the flip-flops and the reset polarity is based on fault-propagation analysis, which determines the impact of a selected flip-flop on fault propagation from the circuits structure. Application of partial reset as described above yields an average improvement of 15% in fault-coverage for sequential circuits resistant to random pattern testing. To further enhance testability, we also present a methodology for selecting observable test points based on propagation of switching activity. Overall, high fault coverages (about 97%) are obtained for many of the ISCAS89 benchmark circuits. Thus, partial reset BIST provides a low cost alternative for testing sequential circuits when scan design is unacceptable due to area and/or delay constraints. The routing overhead for implementing BIST is seen to be about 6%.     

Design for Delay Testability in High-Speed Digital ICs

The cost-effective testing of high-speed digital ICs is becoming increasingly problematic. Even advanced, costly testers are not always capable of testing these ICs because of their high-speed limitations. This paper focuses on a Design for Delay Testability (DfDT) technique such that high-speed ICs can be tested using inexpensive, low-speed test systems. Also extensions for possible full BIST of delay faults are addressed.     

Testing analog circuits using spectral analysis

In this work a test strategy for analog circuits based on spectral analysis is proposed. The test strategy is blind, in the sense that only statistical information about the input signal is needed, but no sampling of the input signal is required. This feature allows the test of analog circuits with minimum analog hardware addition. In the context of Systems-on-Chip, this strategy needs only the inclusion of a small random signal generator, and transfers most of the signal processing to the digital domain, allowing the use of a purely digital tester or a digital BIST technique. This paper presents the underlying principle of the method and experimental test results for linear analog systems.     

A Low-Cost At-Speed BIST Architecture for Embedded Processor and SRAM Cores

We have introduced a low-cost at-speed BIST architecture that enables conventional microprocessors and DSP cores to test their functional blocks and embedded SRAMs in system-on-a-chip architectures using their existing hardware and software resources. To accommodate our proposed new test methodology, minor modifications should be applied to base processor within its test phase. That is, we modify the controller to interpret some of the instructions differently only within the initial test mode. In this paper, we have proposed a fuctional self-test methodology that is deterministic in nature. In our proposed architecture, a self test program called BIST Program is stored in an embedded ROM as a vehicle for applying tests. We first start with testing processor core using our proposed architedture. Once the testing of the processor core is completed, this core is used to test the embedded SRAMs. A test algorithm which utilizes a mixture of existing memory testing techniques and covers all important memory faults is presented in this paper. The proposed memory test algorithm covers 100% of the faults under the fault model plus a data retention test. The hardware overhead in the proposed architecture is shown to be negligible. This architecture is implemented on UTS-DSP (University of Tehran and Iran Communicaton Industries (SAMA)) IC which has been designed in VLSI Circuits and Systems Laboratory.     

Deterministic built-in test pattern generation for high-performancecircuits using twisted-ring counters

We present a new approach for built-in test pattern generation based on the reseeding of twisted-ring counters (TRCs). The proposed technique embeds a precomputed deterministic test set for the circuit under test (CUT) in a short test sequence produced by a TRC. The TRC is designed using existing circuit flip-flops and does not add to hardware overhead beyond what is required for basic scan design. The test control logic is simple, uniform for all circuits, and can be shared among multiple CUTs. Furthermore, the proposed method requires no mapping logic between the test generator circuit and the CUT; hence it imposes no additional performance penalty. Experimental results for the ISCAS benchmark circuits show that it is indeed possible to embed the entire precomputed test set in a TRC sequence using only a small number of seeds