Iddq test coverage in software

May 27, 2019 decision coverage criteriadc for software testing. The continuing research is focussed on developing techniques for achieving and evaluating high security and reliability in computational systems. Iddq test pattern stuckat fault pattern pseudo stuckat fault pattern table 1. It will include gathering information about which parts of a program are executed when running the test suite to determine which branches of conditional statements have been taken. In cmos, there are some defects which do not affect the. It has been used for many years by a few companies and is now receiving wider acceptance as an industry tool. In order to ensure complete condition coverage criteria for the above example, a, b and c should be evaluated at least once against true and false. Test coverage and code quality are two of a handful of fundamental metrics used to analyse, track and measure the effectiveness of an it project or initiative. We can use test management tools to perform functional test coverage which will establish traceability between, requirements, defects and test cases. It catches some defects that other tests, particularly stuckat logic tests, do not. Edn iddq testing to improve yield and reliability, 12. The test software doesnt need to understand the function of the logicit just tries to exercise the logic segments observed by a scan cell. The use of iddq testing provides significant improvement of test coverage, forcing some design restrictions.

Through iddq, we can achieve 100% fault coverage using less current strobes. The range of currents is quite large and can go as low as 50 na. Aitken iddq testing as a component of a test suite. It helps in evaluating the effectiveness of testing by providing data on different. Quiescent power supply current i ddq testing of cmos integrated circuits is a technique for production quality and reliability improvement, design validation, and failure analysis. These topics have moved from the experimental phase into mainstream test and are now introduced in this course. The voltages and currents requirements vilvih, iolioh, vdd are different in conventional function than those in iddq. The selection criteria should be set up in such a way that by using less iddq strobes, we can get more test coverage. Embodiments of the iddq test routine described herein can cover the entire functional digital part of an ic chip. This paper describes the present status of iddq testing along with the essential items and necessary data related to iddq.

Finegrained multithreading across multiple cores overcomes memory bottlenecks. Test coverage is an important indicator of software quality and an essential part of software maintenance. The impact of the threshold on the defect coverage is. In addition to the tried and true test methodologies of the past, engineers must now understand topics such as defect oriented testing, fault coverage, designfortestability, iddq and structural test. So, in our example, the 3 following tests would be. The atpg tool then uses the fault models to determine the patterns required to detect those faults at all points in the circuit or almost all. To achieve higher fault coverage with cmos vlsi ics, another test method. These topics have moved from the experimental phase into mainstream test. These circuits are usually tested as a way to find different types of manufacturing faults. Hence, typically, only 23 test vectors are sufficient to achieve a 50% fault coverage for i ddq testing. Summary of test patterns used for experiment one of the purposes of our experiment is to evaluate an actual number of fails using a test vehicle asic design, to obtain base data for calculating defect level in our new test method. Extending the pseudostuckat fault model to provide.

Firstly, a high test coverage is not a sufficient measure of effective testing. A chip consuming a chip consuming more current than the threshold i ddq fail chip can still pass all functional tests. One can thus achieve condition testing coverage by running the following five test cases for example. I ddq tests require an offchip current monitoring device, in addition to the ate. A practical method to increase test coverage using iddq. Scan and atspeed testing require ate automatic test equipment to apply test patterns and receive the output of the dut device under test. Technical articles on basic electrical techniques in the proceedings, tutorials, and workshops of the international test conference, international symposium for testing and failure analysis, and international reliability physics symposium.

Aug 07, 2014 the selection criteria should be set up in such a way that by using less iddq strobes, we can get more test coverage. It relies on measuring the supply current idd in the. We can use bi directional traceability matrix to achieve test coverage. The iddq test takes relatively long time since many static states must be covered. This test is long, because some stabilisation time is required to measure the leakage with the same repatibility. It means that each decision must have at least one true and one false value. Decision coverage or branch coverage is a testing method, which aims to ensure that each one of the possible branch from each decision point is executed at least once and thereby ensuring that all reachable code is executed. The diagram below illustrates the idea of performing low iddq current measurements. Keithley iv tracer software uses the touchscreen interface of. Test coverage is a function of where the iddq test limit is set. Each of the the b0, b1, b2, b3 shows up at least once with true and at least once with false. Ic counterfeits come from all around the world and consolidated by various electronics distributors.

For instance, one of the ways we measure code quality is by looking at corresponding test coverage. Halting a functional test and making a precise current measurement at thousands of states will result in test times which are unacceptable in a manufacturing environment. Iddq patterns in our previous test method did not give the best result in terms of the pattern efficiency, as they are generated as regular static tests i. The results show that iddq testing can detect some types of defects in precharge and. With the available data, it appears that more than 95% fault coverage can be achieved costeffectively by adding iddq test set of about 20 vectors to the functional and stuckat test set with 80%. How much test coverage is enough for your testing strategy. These methods are capable of high fault coverage while the test application time is rather short, thus creating a promising test approach for primary fault screening. However, we have found it is possible to set the limit so low that no parts will pass. This choice is a tradeoff between test coverage and test time. The block diagram of iddq scanning dft solution is shown in figure 1. The tester s software uses a functional test set to drive the dut s. Reduces test time and test cost improves product quality improves test quality accelerates failure analysis ridgetop europe develops and supports the qstar test product line for iddqissqiddt and other test methodologies. Test coverage metrics to measure the code quality reqtest.

The term code coverage refers to the degree to which the source code in a program, subprogram, or function is tested by a test suite. Ideas, examples, problems and prospects in computer program testing ed. Highly optimized, memoryefficient test generation, and fault simulation engines for orderofmagnitude faster atpg runtime compared to previous technologies. Iso 26262 functional safety semiconductor engineering. The need for several fault coverage metrics, journal of elect. Since scan test modifies flip flops that are already in the design to enable them to also act as scan cells, the impact of the test circuitry is relatively small, typically adding about only 15% to the. Both test coverage and code quality are interlinked in a way few other metrics are. Functional test, or ate, is a highly flexible and configurable method for a wide range of devices. On the contrary, test coverage more accurately gives a measure of the extent to which the code has not been tested. Leakage current iddq test 56 is a defectbased test that measures device. Cadence modus dft software solution reduce test time by up to 3x without impact to fault coverage or chip size the cadence modus dft software solution is a comprehensive nextgeneration physically aware designfortest dft, automatic test pattern generation atpg, and silicon diagnostics tool. Citeseerx document details isaac councill, lee giles, pradeep teregowda. A test suite which provides high code coverage for a program more thoroughly tests its source code and reduces the chance of the program containing software bugs more than a test suite that provides low code. E, reliability of the path analysis testing strategy, ieee transactions on software engineering, vol 2, no 3 sept 1976,pp 28215.

This method relies on measuring the supply current idd in its. To enable automatic test pattern generation atpg software to create the test patterns, fault models are defined that predict the expected behaviors response from the ic when defects are present. All verilog, asic and systems designers, foundries, and ip developers. The iddq test is to measure the leakage of the chip at each stop point inside the patterns. Decision coverage and condition coverage have no subsumption relationship. Mar 31, 2016 iddq testing is one of the many ways to test cmos integrated circuits in production. Bics built in current sensor, amux analog multiplexer and test control circuit. In some test cases, we do not care about a given value as it has no influence on the condition whose output we want to get right. An embodiment of a method includes applying a test pattern of inputs to a device, the device including one or more cmos complementary metal oxide semiconductor transistors, and obtaining current measurements for the device, each of the current measurements being a measurement of a current after applying an input of the test pattern to the device. The new tool uses the pseudo stuckat fault model, and creates more compact iddq patterns, taking. For instance, the use of the faultfree nextstate function for sequential iddq fault simulation is shown to result in a wrong classification of some resistive short defects. Design for testability for soc based on iddq scanning. According to decision coverage criteriadc criteria, every decision must be covered.

It is little more than 15years since the idea of iddq testing was first proposed. The iddq test routine can be repeated periodically, such as in different states during operation or at different positions in a firmwaredefined flow, in order to increase the test coverage. Apr 29, 2020 test coverage is defined as a metric in software testing that measures the amount of testing performed by a set of test. Pdf iddq testing experiments for various cmos logic design. A test case is an input on which the program under test is executed during testing. As shown in the figure, the testmeasurement circuitry consists of tree blocks. It is a simple and direct test that can identify physical defects. That is, every decision is taken each way, true and false. Such a problem can lead to overestimate the fault coverage achieved by means of iddq testing. Iso 26262 consists of the following parts, under the general title road vehicles.

Jun, 2014 the term code coverage refers to the degree to which the source code in a program, subprogram, or function is tested by a test suite. However, it is noticed that observing the average transient current can lead to improvements in real defect coverage, which is referred to iddt testing. The iddq test increases the probability of open circuit defect. Test application time is fast since the vector sets are small. Many semiconductor companies now consider iddq testing as an integral part of the overall testing for all ics.

Iddq testing to improve yield and reliability, 12 edn. Quiescent power supply current iddq testing of cmos integrated circuits is a technique for production quality and reliability improvement, design validation, and failure analysis. Bics builtin current sensor, amux analog multiplexer and test control circuit. The software can select a small number of test vectors for iddq testing from the. The basic idea is to implement iddq scan chain for separate blocks block under test, but in fig. It provides additional test coverage, beyond the coverage of conventional tests and. Iddq testing is a method for testing cmos integrated circuits for the presence of manufacturing faults.

In software testing practice, testers are often required to generate test cases to execute every statement in the program at least once. It has high test coverage and its capable of replicating oem testing for 100% test coverage. A program with high test coverage, measured as a percentage, has had more of its source code executed during testing, which suggests it has a lower chance of containing undetected software bugs compared to a program with low test coverage. Iso 26262 is a standard related to the safety of electrical and electronic systems within a car and addresses possible hazards caused by malfunctioning behavior of safetyrelated systems, including interaction of these systems. In production tests, typically only a few logic states are chosen to apply the i ddq test. In computer science, test coverage is a measure used to describe the degree to which the source code of a program is executed when a particular test suite runs. Usually up to 3040 test points are needed for a 80% toggle iddq coverage. As shown in the figure, the test measurement circuitry consists of tree blocks. This is the first systematic study of iddq testing of resistive short defects. Iddq testing is one of the many ways to test cmos integrated circuits in production. Here we seek to illustrate the basic notions underlying adequacy criteria.

Digital test methods iddq tutorial the iddq timing is not set to run at the max specified frequency all the times due to test method constrains. Qstar test is a complete line of affordable precision current measurement modules and intellectual property ip for ic testing that. For many manufacturers, there is a concern some of these devices are not the best quality and may have been used before in the. Best practices of test coverage in software testing. Ic counterfeit detection with curve tracers robson.

It helps in validating all the branches in the code making. Looking for online definition of iddq or what iddq stands for. Fault coverage improvement by adding a small iddq test. Condition coverage is also known as predicate coverage in which each one of the boolean expression have been evaluated to both true and false. Iddq test differs from a functional test in that there is no inherent passfail condition. Deltaiddq testing of resistive short defects semantic. What is condition testing as defined by the istqb syllabus. Iddq tests were therefore performed on a portion of the functional vectors, often. This means that if we have a low test coverage metric, then we can be sure that there are significant portions of our code that are not tested. Iddq is listed in the worlds largest and most authoritative dictionary database of abbreviations and acronyms. Cmos always has a negative impact on the maximum iddq test coverage that is.

Identical test coverage and pattern reduction across different server configurations and machines for. In general, the lower this limit, the better the coverage. Hence, the test quality assessment is invalidated, because it is optimistic. Electric faults can be a major hazard and it can even lead to fatalities. No additional test generation effort or software is required.