The automobile is a rough environment for electronics. Not only must the electronics operate over a wide temperature, the supply voltages can also vary such as when devices such as the starter motor are operated.
These noise signals are often used to test how well the electronics cope with them, but using standard test waveforms often do not catch problems, because using a standard waveform is only one of many different noise signals that an automotive electronic control unit (ECU) or the network may encounter. Depending on how a vehicle is operated only specific instances may cause an ECU to fail.
The solution to this dilemma is to break down a standard test waveform into its component parts and then randomly vary the voltage and time parameters of those components. By running a functional test while applying each of these variations, you have a better chance of finding the exact combination that will cause problems in the field and ensure that your electrical systems are robust, comply to standards as well as those situations not covered by standards tests. Exhaustive testing with random test waveforms can help you find those unexpected circumstances that testing only with standard test waveforms will not detect.
Breaking down a test waveform
Our LVTGO solves this problem using the typical test waveform shown in the Figure below. This waveform simulates how the battery supply voltage might vary when a driver starts an engine or how the voltage varies in a start/stop environment. As you can see, we’ve assigned variables to the significant voltage values—U0 through U7—and the time values—T0 through T9. These parameters can then be assigned minimum and maximum values as well as a step size.
Generating random test waveforms
Once we have assigned these variables to points on the test waveform, the LVTGO randomly assigns actual values to them. A pseudo-random sequence is recommended since it is truly random but is completely repeatable. Repeatability is important, since you want to be able to reproduce problem waveforms in order to troubleshoot the problem.
Exhaustive testing lowers costs
Costs are significantly lowered by finding errors or failures of cars’ electronics in the lab before releasing to the field. By running hundreds or thousands of tests while randomly varying each voltage waveform parameter from minimum to maximum, you perform an exhaustive test of the ECU, the network or the entire vehicle. Using this technique, the ECU will experience in the lab nearly all of the supply voltage conditions that it will experience in the field. Tests can be run overnight, over a weekend or longer.
All LVTGO models include exhaustive testing as standard. Randomization is about testing for those unexpected conditions that normally are not tested for and, therefore, not found.
Randomization test techniques are a major addition to traditional standards testing for low voltage testing and produce more robust electronics and fewer field failures.