BIST Architecture Research Articles

A Programmable Built-in Self-Test for Embedded Memory Cores

A memory test algorithm for detecting neighborhood pattern sensitive faults (NPSFs), including static NPSF (SNPSF), passive NPSF (PNPSF) and active NPSF (ANPSF), is proposed in this paper. The patterns can also detect all the traditional faults present in the memory array such as stuck-at faults (SAFs), transition faults (TFs), coupling faults (CFs) and address decoder faults. Next, a programmable BIST architecture is designed. The BIST circuit allows the users to select a vast variety of test algorithms based on their choice. The single BIST circuit is capable of testing different types of memory cores embedded in SOC. The proposed BIST circuit is shared among the different memory cores in an SOC. For this purpose, test wrappers for the shared BIST circuits and the memory cores are designed. Finally, a test scheduling algorithm is developed to reduce the overall test time.

An Efficient BIST Architecture for Delay Faults in the Logic Cells of Symmetrical SRAM-Based FPGAs

The objective of this paper is to propose a BIST scheme enabling the test of delay faults in all the Look-Up Tables (LUTs) of FPGA SRAMs, in a Manufacturing context. The BIST scheme does not consume any area overhead and can be removed from the device after the test thus, allowing the use of the whole circuit by the user. The structure we propose is composed of a simple test pattern generator, an error detector and a chain of LUTs. The chain of LUTs is formed alternatively by a LUT and a flip---flop. By using such a chain, the test of all delay faults in every LUT is enabled. In this paper, we develop an experiment based on the implantation of our BIST architecture in a Virtex FPGA from Xilinx. The purpose of this experiment is to show the feasibility of our solution. As a result, one important issue from this solution is its ability to detect the "smallest" delay faults in the LUTs, i.e. the smallest delays that can be observed on a LUT output.

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 ATEs 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.

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.

Behavioral test generation for the selection of BIST logic

The identification of the most suited BIST architecture is one of the bottlenecks in the actual application of self-testing techniques. The aim of this paper is the investigation of possible relations between the behavioral level specification of the circuit, and the structural level, where BIST logic is inserted. We propose to use behavioral test patterns to guide the selection of the most appropriate BIST architecture with respect to the given application as a trade-off between fault coverage and area overhead. The correlation between the behavioral analysis and the actual fault coverage of the inserted BIST logic has been shown on a number of benchmarks.

SRAM transparent testing methodology using dynamic power supply current

A new transparent testing methodology using dynamic power supply current is proposed which is much simpler than traditional transparent testing algorithms. It employs the dynamic power supply current instead of making signatures so that it does not need the extra steps and hardware to generate a signature. The paper describes how to convert a March algorithm to a transparent one and how to cover the fault models considered. The transformed algorithm is much simpler and test time can be greatly reduced. In addition, it can detect extra faults that the original algorithm cannot. The whole BIST architecture is described, together with a new peak current detector.

A Low-Cost BIST Architecture for Linear Histogram Testing of ADCs

This paper investigates the viability of an ADC BIST scheme for implementing the histogram test technique. An original approach is developed to extract the ADC parameters from the histogram with a minimum area overhead. In particular, it is shown that the choice of a triangle-wave input signal combined with an appropriate time decomposition technique of the test procedure permits to drastically reduce the required on-chip hardware circuitry.

Distributed BIST Architecture to Combat Delay Faults

To successfully combat delay faults there is an urgent need for a proper design for testability (DFT). The foundation of any DFT methodology rests on its scan design. This paper describes three versions of a new design of a shift register latch that lend themselves to distributed self-test and delay test. The advantages of this new SRL is faster application of test vectors, higher DC and AC fault coverages, with low performance impact. Adoption of this new DFT methodology brings us closer to the ideal target of one test-per-clock as opposed to one test-per-scan. Operation, cost, and other attributes are studied in detail. Results of adopting one of these SRLs are reported on ten pilot chips.

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.