Iddq test coverage in software

It means that each decision must have at least one true and one false value. Firstly, a high test coverage is not a sufficient measure of effective testing. So, in our example, the 3 following tests would be. 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.

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. 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 chip consuming a chip consuming more current than the threshold i ddq fail chip can still pass all functional tests. It has high test coverage and its capable of replicating oem testing for 100% test coverage. The test software doesnt need to understand the function of the logicit just tries to exercise the logic segments observed by a scan cell. 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.

How much test coverage is enough for your testing strategy. We can use bi directional traceability matrix to achieve test coverage. 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. Decision coverage and condition coverage have no subsumption relationship.

Ic counterfeits come from all around the world and consolidated by various electronics distributors. Finegrained multithreading across multiple cores overcomes memory bottlenecks. This is the first systematic study of iddq testing of resistive short defects. Such a problem can lead to overestimate the fault coverage achieved by means of iddq testing. 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. To achieve higher fault coverage with cmos vlsi ics, another test method. Bics builtin current sensor, amux analog multiplexer and test control circuit. Citeseerx document details isaac councill, lee giles, pradeep teregowda. Wakerly digital design,principles and practices,second edition,prentice hall,1994. It will include gathering information about which parts of a program are executed when running the test suite to determine which branches of. It has been used for many years by a few companies and is now receiving wider acceptance as an industry tool.

The diagram below illustrates the idea of performing low iddq current measurements. Through iddq, we can achieve 100% fault coverage using less current strobes. Test coverage is an important indicator of software quality and an essential part of software maintenance. The need for several fault coverage metrics, journal of elect. 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. 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.

The use of iddq testing provides significant improvement of test coverage, forcing some design restrictions. One can thus achieve condition testing coverage by running the following five test cases for example. In cmos, there are some defects which do not affect the. 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. 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. Both test coverage and code quality are interlinked in a way few other metrics are. 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. As shown in the figure, the testmeasurement circuitry consists of tree blocks. No additional test generation effort or software is required. Iddq is listed in the worlds largest and most authoritative dictionary database of abbreviations and acronyms. 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. Test coverage is defined as a metric in software testing that measures the amount of testing performed by a set of test. Mar 31, 2016 iddq testing is one of the many ways to test cmos integrated circuits in production.

The iddq test increases the probability of open circuit defect. Aitken iddq testing as a component of a test suite. The range of currents is quite large and can go as low as 50 na. 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%. 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. 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. Design for testability for soc based on iddq scanning. Cmos always has a negative impact on the maximum iddq test coverage that is. Iddq testing is one of the many ways to test cmos integrated circuits in production. 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. Hence, the test quality assessment is invalidated, because it is optimistic. 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. 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.

Extending the pseudostuckat fault model to provide. Best practices of test coverage in software testing. 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. Ideas, examples, problems and prospects in computer program testing ed. For instance, one of the ways we measure code quality is by looking at corresponding test coverage. Bics built in current sensor, amux analog multiplexer and test control circuit. However, we have found it is possible to set the limit so low that no parts will pass. That is, every decision is taken each way, true and false. Ic counterfeit detection with curve tracers robson. Here we seek to illustrate the basic notions underlying adequacy criteria. The impact of the threshold on the defect coverage is. Iddq testing has progressed to become a worldwide accepted test method to detect cmos ic defects. In software testing practice, testers are often required to generate test cases to execute every statement in the program at least once. The tester s software uses a functional test set to drive the dut s.

Scan and atspeed testing require ate automatic test equipment to apply test patterns and receive the output of the dut device under test. The iddq test is to measure the leakage of the chip at each stop point inside the patterns. This choice is a tradeoff between test coverage and test time. E, reliability of the path analysis testing strategy, ieee transactions on software engineering, vol 2, no 3 sept 1976,pp 28215. Iddq test pattern stuckat fault pattern pseudo stuckat fault pattern table 1. 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. These topics have moved from the experimental phase into mainstream test. 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. Qstar test is a complete line of affordable precision current measurement modules and intellectual property ip for ic testing that. 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. Iddq testing is a cost effective test strategy for digital cmos ics with the.

The selection criteria should be set up in such a way that by using less iddq strobes, we can get more test coverage. I ddq tests require an offchip current monitoring device, in addition to the ate. Keithley iv tracer software uses the touchscreen interface of. This test is long, because some stabilisation time is required to measure the leakage with the same repatibility. May 27, 2019 decision coverage criteriadc for software testing. Iddq testing is a method for testing cmos integrated circuits for the presence of manufacturing faults. Functional test, or ate, is a highly flexible and configurable method for a wide range of devices. 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. Looking for online definition of iddq or what iddq stands for. The new tool uses the pseudo stuckat fault model, and creates more compact iddq patterns, taking. 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. Iddq tests were therefore performed on a portion of the functional vectors, often. For many manufacturers, there is a concern some of these devices are not the best quality and may have been used before in the. Each of the the b0, b1, b2, b3 shows up at least once with true and at least once with false.

It is little more than 15years since the idea of iddq testing was first proposed. 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. The continuing research is focussed on developing techniques for achieving and evaluating high security and reliability in computational systems. 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. Test application time is fast since the vector sets are small. 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. Iddq testing to improve yield and reliability, 12 edn. 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. In production tests, typically only a few logic states are chosen to apply the i ddq test.

This method relies on measuring the supply current idd in its. The iddq test takes relatively long time since many static states must be covered. Embodiments of the iddq test routine described herein can cover the entire functional digital part of an ic chip. A practical method to increase test coverage using iddq.

Test coverage metrics to measure the code quality reqtest. Iso 26262 functional safety semiconductor engineering. We can use test management tools to perform functional test coverage which will establish traceability between, requirements, defects and test cases. 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 results show that iddq testing can detect some types of defects in precharge and. Usually up to 3040 test points are needed for a 80% toggle iddq coverage. According to decision coverage criteriadc criteria, every decision must be covered.

It provides additional test coverage, beyond the coverage of conventional tests and. Pdf iddq testing experiments for various cmos logic design. 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. On the contrary, test coverage more accurately gives a measure of the extent to which the code has not been tested. All verilog, asic and systems designers, foundries, and ip developers. What is condition testing as defined by the istqb syllabus. Fault coverage improvement by adding a small iddq test. As shown in the figure, the test measurement circuitry consists of tree blocks. Many semiconductor companies now consider iddq testing as an integral part of the overall testing for all ics. Leakage current iddq test 56 is a defectbased test that measures device. 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 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. Condition coverage is also known as predicate coverage in which each one of the boolean expression have been evaluated to both true and false. Edn iddq testing to improve yield and reliability, 12. It relies on measuring the supply current idd in the. It helps in evaluating the effectiveness of testing by providing data on different.

It helps in validating all the branches in the code making. In general, the lower this limit, the better the coverage. It catches some defects that other tests, particularly stuckat logic tests, do not. Quiescent power supply current iddq testing of cmos integrated circuits is a technique for production quality and reliability improvement, design validation, and failure analysis. Highly optimized, memoryefficient test generation, and fault simulation engines for orderofmagnitude faster atpg runtime compared to previous technologies. It is a simple and direct test that can identify physical defects. Electric faults can be a major hazard and it can even lead to fatalities. Identical test coverage and pattern reduction across different server configurations and machines for. 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 block diagram of iddq scanning dft solution is shown in figure 1. 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.

Deltaiddq testing of resistive short defects semantic. Iddq test differs from a functional test in that there is no inherent passfail condition. This paper describes the present status of iddq testing along with the essential items and necessary data related to iddq. These circuits are usually tested as a way to find different types of manufacturing faults. The software can select a small number of test vectors for iddq testing from the. Iso 26262 consists of the following parts, under the general title road vehicles. 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 basic idea is to implement iddq scan chain for separate blocks block under test, but in fig. Hence, typically, only 23 test vectors are sufficient to achieve a 50% fault coverage for i ddq testing. Test coverage is a function of where the iddq test limit is set. Hawkins, iddq testing of vlsi circuits, kluwer academis publishers, 1993.