Iddq test coverage in software

Deltaiddq testing of resistive short defects semantic. It means that each decision must have at least one true and one false value. This method relies on measuring the supply current idd in its. Wakerly digital design,principles and practices,second edition,prentice hall,1994. 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. One can thus achieve condition testing coverage by running the following five test cases for example.

Iddq tests were therefore performed on a portion of the functional vectors, often. The iddq test increases the probability of open circuit defect. These topics have moved from the experimental phase into mainstream test and are now introduced in this course. In general, the lower this limit, the better the coverage. 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. May 27, 2019 decision coverage criteriadc for software testing. To use this measurement in a test program, the device must be static or remain in a particular logic state long enough for a precision current measurement to be made. 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.

Identical test coverage and pattern reduction across different server configurations and machines for. 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. The test software doesnt need to understand the function of the logicit just tries to exercise the logic segments observed by a scan cell. Cmos always has a negative impact on the maximum iddq test coverage that is. The voltages and currents requirements vilvih, iolioh, vdd are different in conventional function than those in iddq. Through iddq, we can achieve 100% fault coverage using less current strobes. Iddq is listed in the worlds largest and most authoritative dictionary database of abbreviations and acronyms. Embodiments of the iddq test routine described herein can cover the entire functional digital part of an ic chip. The iddq test takes relatively long time since many static states must be covered. It has high test coverage and its capable of replicating oem testing for 100% test coverage.

Electric faults can be a major hazard and it can even lead to fatalities. Ic counterfeits come from all around the world and consolidated by various electronics distributors. 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. 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. To achieve higher fault coverage with cmos vlsi ics, another test method. The impact of the threshold on the defect coverage is. Here we seek to illustrate the basic notions underlying adequacy criteria. These circuits are usually tested as a way to find different types of manufacturing faults. 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.

Hence, the test quality assessment is invalidated, because it is optimistic. The diagram below illustrates the idea of performing low iddq current measurements. 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. Ic counterfeit detection with curve tracers robson.

It helps in validating all the branches in the code making. How much test coverage is enough for your testing strategy. 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. Looking for online definition of iddq or what iddq stands for.

As shown in the figure, the test measurement circuitry consists of tree blocks. These topics have moved from the experimental phase into mainstream test. For instance, one of the ways we measure code quality is by looking at corresponding test coverage. In production tests, typically only a few logic states are chosen to apply the i ddq test. 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. All verilog, asic and systems designers, foundries, and ip developers.

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. Extending the pseudostuckat fault model to provide. 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. Many semiconductor companies now consider iddq testing as an integral part of the overall testing for all ics. 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.

Fault coverage improvement by adding a small iddq test. Bics builtin current sensor, amux analog multiplexer and test control circuit. Firstly, a high test coverage is not a sufficient measure of effective testing. However, it is noticed that observing the average transient current can lead to improvements in real defect coverage, which is referred to iddt testing. Both test coverage and code quality are interlinked in a way few other metrics are. 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. Iso 26262 consists of the following parts, under the general title road vehicles. The tester s software uses a functional test set to drive the dut s.

Test coverage is defined as a metric in software testing that measures the amount of testing performed by a set of test. 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. 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. A test case is an input on which the program under test is executed during testing. It is a simple and direct test that can identify physical defects. Test application time is fast since the vector sets are small.

According to decision coverage criteriadc criteria, every decision must be covered. Scan and atspeed testing require ate automatic test equipment to apply test patterns and receive the output of the dut device under test. We can use bi directional traceability matrix to achieve test coverage. 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. Bics built in current sensor, amux analog multiplexer and test control circuit. The results show that iddq testing can detect some types of defects in precharge and. Leakage current iddq test 56 is a defectbased test that measures device. Keithley iv tracer software uses the touchscreen interface of. No additional test generation effort or software is required. This test is long, because some stabilisation time is required to measure the leakage with the same repatibility. 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. For many manufacturers, there is a concern some of these devices are not the best quality and may have been used before in the.

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. The selection criteria should be set up in such a way that by using less iddq strobes, we can get more test coverage. Iddq test pattern stuckat fault pattern pseudo stuckat fault pattern table 1. Decision coverage and condition coverage have no subsumption relationship. Iddq testing is a method for testing cmos integrated circuits for the presence of manufacturing faults. I ddq tests require an offchip current monitoring device, in addition to the ate. The block diagram of iddq scanning dft solution is shown in figure 1. The continuing research is focussed on developing techniques for achieving and evaluating high security and reliability in computational systems. Iddq test differs from a functional test in that there is no inherent passfail condition. 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 testing has progressed to become a worldwide accepted test method to detect cmos ic defects. The use of iddq testing provides significant improvement of test coverage, forcing some design restrictions. Finegrained multithreading across multiple cores overcomes memory bottlenecks. 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. Usually up to 3040 test points are needed for a 80% toggle iddq coverage. The iddq test is to measure the leakage of the chip at each stop point inside the patterns. Test coverage is a function of where the iddq test limit is set. 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. Qstar test is a complete line of affordable precision current measurement modules and intellectual property ip for ic testing that. A practical method to increase test coverage using iddq. 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. Test coverage metrics to measure the code quality reqtest.

It provides additional test coverage, beyond the coverage of conventional tests and. It is little more than 15years since the idea of iddq testing was first proposed. Aitken iddq testing as a component of a test suite. The need for several fault coverage metrics, journal of elect. What is condition testing as defined by the istqb syllabus. 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. This paper describes the present status of iddq testing along with the essential items and necessary data related to iddq. The range of currents is quite large and can go as low as 50 na. The basic idea is to implement iddq scan chain for separate blocks block under test, but in fig. On the contrary, test coverage more accurately gives a measure of the extent to which the code has not been tested. That is, every decision is taken each way, true and false. Design for testability for soc based on iddq scanning. 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.

Sep 28, 2015 we can use test management tools to perform functional test coverage which will establish traceability between, requirements, defects and test cases. 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. Iddq testing is a cost effective test strategy for digital cmos ics with the. 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%. It will include gathering information about which parts of a program are executed when running the test suite to determine which branches of. Iso 26262 functional safety semiconductor engineering. It catches some defects that other tests, particularly stuckat logic tests, do not. We can use test management tools to perform functional test coverage which will establish traceability between, requirements, defects and test cases. Quiescent power supply current iddq testing of cmos integrated circuits is a technique for production quality and reliability improvement, design validation, and failure analysis. So, in our example, the 3 following tests would be. 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. As shown in the figure, the testmeasurement circuitry consists of tree blocks.

In software testing practice, testers are often required to generate test cases to execute every statement in the program at least once. It has been used for many years by a few companies and is now receiving wider acceptance as an industry tool. Best practices of test coverage in software testing. E, reliability of the path analysis testing strategy, ieee transactions on software engineering, vol 2, no 3 sept 1976,pp 28215. Iddq testing is one of the many ways to test cmos integrated circuits in production. Pdf iddq testing experiments for various cmos logic design. Hence, typically, only 23 test vectors are sufficient to achieve a 50% fault coverage for i ddq testing.

Hawkins, iddq testing of vlsi circuits, kluwer academis publishers, 1993. 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. It helps in evaluating the effectiveness of testing by providing data on different. It relies on measuring the supply current idd in the. The new tool uses the pseudo stuckat fault model, and creates more compact iddq patterns, taking. Condition coverage is also known as predicate coverage in which each one of the boolean expression have been evaluated to both true and false. 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. In cmos, there are some defects which do not affect the. Such a problem can lead to overestimate the fault coverage achieved by means of iddq testing. 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.

Mar 31, 2016 iddq testing is one of the many ways to test cmos integrated circuits in production. However, we have found it is possible to set the limit so low that no parts will pass. Highly optimized, memoryefficient test generation, and fault simulation engines for orderofmagnitude faster atpg runtime compared to previous technologies. A chip consuming a chip consuming more current than the threshold i ddq fail chip can still pass all functional tests. Edn iddq testing to improve yield and reliability, 12. The software can select a small number of test vectors for iddq testing from the. Each of the the b0, b1, b2, b3 shows up at least once with true and at least once with false. Test coverage is an important indicator of software quality and an essential part of software maintenance. Iddq testing to improve yield and reliability, 12 edn. This is the first systematic study of iddq testing of resistive short defects. Functional test, or ate, is a highly flexible and configurable method for a wide range of devices. Citeseerx document details isaac councill, lee giles, pradeep teregowda. This choice is a tradeoff between test coverage and test time.