Built-in Self-test Test Pattern Generator Research Articles

A BIST TPG for Low Power Dissipation and High Fault Coverage

In This paper presents a low hardware overhead test pattern generator (TPG) for scan-based built-in self-test (BIST) that can reduce switching activity in circuits under test (CUTs) during BIST and also achieve very high fault coverage with reasonable lengths of test sequences. The proposed BIST TPG decreases transitions that occur at scan inputs during scan shift operations and hence reduces switching activity in the CUT. The proposed BIST is comprised of two TPGs: LT-RTPG and 3- weight WRBIST. Test patterns generated by the LT-RTPG detect easy-to-detect faults and test patterns generated by the 3-weight WRBIST detect faults that remain undetected after LT-RTPG patterns are applied. The proposed BIST TPG does not require modification of mission logics, which can lead to performance degradation. Experimental results for ISCAS’89 benchmark circuits demonstrate that the proposed BIST can significantly reduce switching activity during BIST while achieving 100% fault coverage for all ISCAS’89 benchmark circuits. Larger reduction in switching activity is achieved in large circuits. Experimental results also show that the proposed BIST can be implemented with low area overhead.

A BIST TPG for Low Power Dissipation and High Fault Coverage

This paper presents a low hardware overhead test pattern generator (TPG) for scan-based built-in self-test (BIST) that can reduce switching activity in circuits under test (CUTs) during BIST and also achieve very high fault coverage with reasonable lengths of test sequences. The proposed BIST TPG decreases transitions that occur at scan inputs during scan shift operations and hence reduces switching activity in the CUT. The proposed BIST is comprised of two TPGs: LT-RTPG and 3-weight WRBIST. Test patterns generated by the LT-RTPG detect easy-to-detect faults and test patterns generated by the 3-weight WRBIST detect faults that remain undetected after LT-RTPG patterns are applied. The proposed BIST TPG does not require modification of mission logics, which can lead to performance degradation. Experimental results for ISCAS'89 benchmark circuits demonstrate that the proposed BIST can significantly reduce switching activity during BIST while achieving 100% fault coverage for all ISCAS'89 benchmark circuits. Larger reduction in switching activity is achieved in large circuits. Experimental results also show that the proposed BIST can be implemented with low area overhead.

LT-RTPG: a new test-per-scan BIST TPG for low switching activity

A new built-in self-test (BIST) test pattern generator (TPG) design, called low-transition random TPG (LT-RTPG), is presented. An LT-RTPG is composed of a linear feedback shift register (LFSR), a /spl kappa/-input AND gate, and a T flip-flop. When used to generate test patterns for test-per-scan BIST, it decreases the number of transitions that occur during scan shifting and, hence, decreases switching activity during testing. Various properties of LT-RTPGs are identified and a methodology for their design is presented. Experimental results demonstrate that LT-RTPGs designed using the proposed methodology decrease switching activity during BIST by significant amounts while providing high fault coverage.

BIST TPG for Combinational Cluster Interconnect Testing at Board Level

A novel built-in self-test (BIST) architecture and a test pattern generator (TPG) design methodology to program this architecture are presented for inter-IC interconnects among combinational non-boundary scan ICs (often called cluster-ICs) via IEEE 1149.1 boundary scan architecture (BSA). Due to the expense and complexity of BSA circuitry, cluster-ICs are still widely used in modern circuit boards. Since combinational logic and 3-state cluster nets exist within cluster interconnect, in order to test all detectable faults in inter-IC nets that include cluster-ICs, newly identified TPG requirements are used to guarantee fault coverage during the design of proposed BIST architecture. This architecture contains a two-level C-TPG that generates constrained pseudo-random patterns for boundary scan cells (BSCs) of cluster control cones, a D-TPG that generates patterns for BSCs of cluster data cones, and a look-up table which is programmed to select, for each BSC, a specific C-TPG or D-TPG stage whose content is shifted into that BSC. This test architecture provides a true BIST solution for cluster testing. The proposed methodology generates TPGs that (i) guarantee the avoidance of multi-driver conflicts when testing via BSA, (ii) guarantee the detection of all testable interconnect faults, (iii) have low area overheads, and (iv) have short test lengths.

Efficient BIST TPG design and test set compaction via input reduction

A new technique called input reduction is proposed for built-in self test (BIST) test pattern generator (TPG) design and test set compaction. This technique analyzes the circuit function and identifies sets of compatible and inversely compatible inputs; inputs in each set can be combined into a test signal in the test mode without sacrificing fault coverage, even if they belong to the same circuit cone. The test signals are used to design BIST TPGs that guarantee the detection of all detectable stuck-at faults in practical test lengths. A deterministic test set generated for the reduced circuit obtained by combining inputs into test signals is usually more compact than that generated for the original circuit. Experimental results show that BIST TPGs based on input reduction achieve complete stuck-at fault coverage in practical test lengths (/spl les/2/sup 30/) for many benchmark circuits. These are achieved with low area overhead and performance penalty to the circuit under test. Results also show that the memory storage and test application time for external testing using deterministic test sets can be reduced by as much as 85%.

BIST test pattern generator for delay testing

To detect delay faults in a digital circuit requires a test sequence applied at the nominal frequency of the circuit. Built-in self-test (BIST) is a technique that provides such testing possibilities at speed, without expensive test equipments. A BIST test pattern generator (TPG) design, targeting the detection of delay faults is proposed.

BIST test pattern generators for two-pattern testing-theory and design algorithms

Testing for delay and CMOS stuck-open faults requires two-pattern tests, and typically a large number of two pattern tests are needed. Built-in self-test (BIST) schemes are attractive for comprehensive testing of such faults. BIST test pattern generators (TPGs) for two-pattern testing, should be designed to ensure high transition coverage. In this paper, necessary and sufficient conditions to ensure complete/maximal transition coverage for linear feedback shift register (LFSR) and cellular automata (CA) have been derived. The theory developed here identifies all LFSR/CA TPGs that maximize transition coverage under any given TPG size constraint. It is shown that LFSRs with primitive feedback polynomials with large number of terms are better for two-pattern testing. Also, CA are shown to be better TPGs than LFSRs for two pattern testing, independent of their feedback rules. Based on the necessary sufficient conditions, efficient algorithms to design optimal TPGs for two-pattern testing have been developed. Experiments on benchmark circuits indicate that TPGs designed using the procedures outlined in this paper obtain high robust path delay fault coverage in short test lengths.

Design of efficient BIST test pattern generators for delay testing

Conventional built-in self-test (BIST) test pattern generators (TPGs) are designed to maximize stuck-at fault coverage in combinational circuits. Such TPGs often provide inadequate coverage of two-pattern tests which are required for the detection of delay faults. In this paper, theoretical results and procedures are presented to design efficient TPGs that ensure high two-pattern coverage for comprehensive delay testing of a circuit under test (CUT). First, new concepts particular to delay testing are identified and exploited to design efficient TPGs based on interleaved cyclic codes. A new concept of test cones is then introduced to further reduce the test length. Finally, the proposed procedures are used to design TPGs for delay testing of ISCAS'89 benchmark circuits and the results demonstrate their effectiveness.

Zero-aliasing for modeled faults

When using built-in self-test (BIST) for testing VLSI circuits the circuit response to an input test sequence, which may consist of thousands to millions of bits, is compacted into a signature which consists of only tens of bits. Usually a linear feedback shift register (LFSR) is used for response compaction via polynomial division. The compacting function is a many-to-one function and as a result some erroneous responses may be mapped to the same signature as the good response. This is known as aliasing. In this paper we deal with the selection of a feedback polynomial for the compacting LFSR, such that an erroneous response resulting from any modeled fault is mapped to a signature that is different from that for the good response. Such LFSRs are called zero-aliasing LFSRs. Only zero-aliasing LFSRs with primitive or irreducible feedback polynomials are considered due to their suitability for BIST test pattern generation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>