A Unified DFT Approach for BIST and External Test

This paper presents a partial reset technique for testability improvement of non-scan sequential circuits. Both pseudo-random BIST and deterministic External Test are in the scope of this paper. The partial reset technique is used to improve hard-to-detect fault activation. This DFT approach is completed with classical insertion of observation points in order to improve fault propagation. Numerous experimental results on ISCAS'89 benchmark circuits show that 100% fault efficiency can be achieved at low cost.     

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.     

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.     

Integration of partial scan and built-in self-test

Partial-Scan based Built-In Self-Test (PSBIST) is a versatile Design for Testability (DFT) scheme, which employs pseudo-random BIST at all levels of test to achieve fault coverages greater than 98% on average, and supports deterministic partial scan at the IC level to achieve nearly 100% fault coverage. PSBIST builds its BIST capability on top a partial scan structure by adding a test pattern generator, an output data compactor, and a PSBIST controller in a way similar to that of deriving a full scan BIST from a full scan structure. However, to make the scheme effective, there is a minimum requirement regarding which flip-flops in the circuit should be replaced by scan flip-flops and/or initialization flip-flops. In addition, test arents are usually added to boost the fault coverage to the range of 95 to 100 percent. These test points are selected based on a novel probabilistic testability measure, which can be computed extremely fast for a special class of circuits. This ciass of circuits is precisely the type of circuits that we obtain after replacing some of the flip-flops.withscan and/or initilization flip-flops. The testability measure is also used for a very useful quick estimation of the fault coverage right after the selection of sean flip-flops, even before the circuit is modified to incorporate PSBIST capability. While PSBIST provides all the benefits of BIST, it incurs lower area overhead and performance degradation than full scan. The area overhead is further reduced when the boundary scan cells are reconfigured for BIST usage.     

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.     

基于March X算法的SRAM BIST的设计

针对LS-DSP中嵌入的128kb SRAM模块,讨论了基于March X算法的BIST电路的设计.根据SRAM的故障模型和测试算法的故障覆盖率,讨论了测试算法的选择、数据背景的产生:完成了基于March X算法的BIST电路的设计.128kb SRAM BIST电路的规模约为2000门,仅占存储器面积的1.2%,故障覆盖率高于80%.     

Delay Fault Testing: Choosing Between Random SIC and Random MIC Test Sequences

The combination of higher quality requirements and sensitivity of high performance circuits to delay defects has led to an increasing emphasis on delay testing of VLSI circuits. In this context, it has been proven that Single Input Change (SIC) test sequences are more effective than classical Multiple Input Change (MIC) test sequences when a high robust delay fault coverage is targeted. In this paper, we show that random SIC (RSIC) test sequences achieve a higher fault coverage than random MIC (RMIC) test sequences when both robust and non-robust tests are under consideration. Experimental results given in this paper are based on a software generation of RSIC test sequences that can be easily generated in this case. For a built-in self-test (BIST) purpose, hardware generated RSIC sequences have to be used. This kind of generation will be shortly discussed at the end of the paper.     

On Using Twisted-Ring Counters for Test Set Embedding in BIST

We present a novel built-in self-test (BIST) architecture for high-performance circuits. The proposed approach is especially suitable for embedding precomputed test sets for core-based systems since it does not require a structural model of the circuit, either for fault simulation or for test generation. It utilizes a twisted-ring counter (TRC) for test-per-clock BIST and is appropriate for high-performance designs because it does not add any mapping logic to critical functional paths. Test patterns are generated on-chip by carefully reseeding the TRC. We show that a small number of seeds is adequate for generating test sequences that embed complete test sets for the ISCAS benchmark circuits.Instead of being stored on-chip, the seed patterns can also be scanned in using a low-cost, slower tester. The seeds can be viewed as an encoded version of the test set that is stored in tester memory. This requires almost 10X less memory than compacted test sets obtained from ATPG programs. This allows us to effectively combine high-quality BIST with external testing using slow testers. As the cost of high-speed testers increases, methodologies that facilitate testing using slow testers become especially important. The proposed approach is a step in that direction.     

FPGA逻辑资源重配置测试技术研究

针对FPGA的逻辑资源测试,提出了一种内建自测试方法.测试中逻辑资源划分为不同功能器件,对应各个功能器件设计了相应的BIST测试模板.在此基础上进一步利用FPGA的部分重配置性能优化BIST测试过程,最终在统一的BIST测试框架下,采用相对较少的配置次数完成了逻辑资源固定故障的全覆盖测试.     

A Method for Trading off Test Time, Area and Fault Coverage in Datapath BIST Synthesis

This paper presents a partitioned and embedded BIST technique for data path like circuits. The BIST scheme is defined at behavioral level for full optimization of both system and BIST modes during High Level Synthesis. Test time, area overhead and fault coverage are under the scope of the method. User-given constraints on fault coverage to achieve on data path operators and on test time are used to guide the BIST insertion technique towards the lowest area overhead solution.     

基于扫描链结构重组的低功耗BIST方案

设计了一种改进扫描链结构的内建自测试(BIST)方案.该方案将设计测试序列发生器(TPG)中合适的n状态平滑器与扫描链的重新排序结合起来,从而达到低功耗测试且不致丢失故障覆盖率的目的.通过对15位随机序列信号的测试,发现此TPG中的n状态平滑器在降低功耗的同时还减小了故障覆盖率,遂又设计了重组扫描链的结构来解决这一问题.实验结果表明,该设计方案对于降低平均测试功耗和提高故障覆盖率都具有显著的效果.     

Partial scan flip-flop selection by use of empirical testability

Partial serial scan as a design for testability technique permits automatic generation of high fault coverage tests for sequential circuits with less hardware overhead and less performance degradation than full serial scan. The objective of the partial scan flip-flop selection method proposed here is to obtain maximum fault coverage for the number of scan flip-flops selected. Empirical Testability Difference (ETD), a measure of potential improvement in the testability of the circuit, is used to successively select one or more flip-flops for addition or deletion of scan logic. ETD is calculated by using testability measures based on empirical evaluation of the circuit with the acutal automatic test pattern generation (ATPG) system. In addition, once such faults are known, ETD focuses on the hard-to-detect faults rather than all faults and uses heuristics to permit effective selection of multiple flip-flops without global optimization. Two ETD algorithms have been extensively tested by using FASTEST ATPG [1, 2] on fourteen of the ISCAS89 [3] sequential circuits. The results of these tests indicate that ETD yields, on average, 35% fewer uncovered detectable faults for the same number of scanned flip-flops or 27% fewer scanned flip-flops for comparable fault coverage relative to cycle-breaking methods.This work was performed while the author was with the University of Wisconsin-Madison.     

A Multi-Mode Scannable Memory Element for High Test Application Efficiency and Delay Testing

This paper introduces a new multi-mode scannable memory element which allows pseudorandom testing to be integrated with scan in sequential circuits without the need of any design changes. As in the case of scan, the new element is used in place of regular flip-flops in the design library. Concurrent with normal operation, the design can accumulate a signature of the state variables in the scan-register configured as a multiple input signature analyzer (MISA). Thus virtually complete state observability is achieved without the need of scanning-out the state for each test-input. The pseudorandom states of the MISA can also be utilized as state inputs in pseudorandom testing. In this way, most faults are covered in a pseudorandom, test per clock mode. Only a few random pattern resistant faults require scan, greatly reducing test application time. Pseudorandom delay testing of the true normally active circuit paths is also possible. Two-pattern tests are supported. Finally, we show that the new memory element can also be used for fault-tolerant design.     

内建自测试的测试生成方法研究

内建自测试（BIST）方法是目前可测试性设计（DFT）中应用前景最好的一种方法,其中测试生成是关系BIST性能好坏的一个重要方面。测试生成的目的在于生成尽可能少的测试向量并用以获得足够高的故障覆盖率,同时使得用于测试的硬件电路面积开销尽可能低、测试时间尽可能短。内建自测试的测试生成方法有多种,文中即对这些方法进行了简单介绍和对比研究,分析了各自的优缺点,并在此基础上探讨了BIST面临的主要问题及发展方向。     

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.     

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.     

Unified built-in self-test for fully differential analog circuits

The reduction of test costs, especially in high safety systems, requires that the same test strategy is employed for design validation, manufacturing and maintenance tests, and concurrent error detection. This unification of off-line and on-line tests has already been attempted for digital circuits and it offers the advantage of serving to all phases of a system lifetime.Market pressure originating from the high costs of analog and mixed signal testing has resulted in renewed efforts for the test of analog parts. In this paper, off-line and on-line test techniques for fully differential analog circuits are presented within an unified approach. The high performance of these circuits makes them very popular for many applications, including high safety, low voltage and high speed systems.A test master compliant with IEEE Std. 1149.1 is described. The Analog Unified BIST (AUBIST) is exemplified for linear and non-linear switched-capacitor circuits. High fault coverage is achieved during concurrent/on-line testing. An off-line test ensures the goal of self-checking circuits and allows the diagnosis of faulty parts. The self-test of the AUBIST circuitry is also considered.This work is part of AMATIST ESPRIT-III Basic Research Project, funded by CEC under contract #8820.     

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.     

An effective BIST scheme for SRAM full speed test

This article presents a novel built-in self-test (BIST) scheme at full speed test where access time test is performed. Based on normal BIST circuits, we harness an all digital phase locked loop to generate a high-frequency clock for static random access memory (SRAM) performance test at full speed. A delay chain is incorporated to achieve the four-phase clock. As inputs to SRAM, clock, address, data are generated in terms of the four-phase clock. Key performance parameters, such as access time, address setup and hold times, are measured. The test chip has been fabricated by United Microelectronics Corporation 55?nm CMOS logic standard process. According to test results, the maximum test frequency is about 1.3?GHz, and the test precision is about 35?ps at the typical process corner with supply voltage 1.0?V and temperature 25°C.