The Fatal Blow

I have to confess being a fan of crime TV shows, particularly ones involving forensics that put together clues and finish by tying it all together and explaining what happened. I like the medical series ‘House’ for the same reason. I wish that I had been blessed with half his diagnostic skills when I was a design engineer. Instead I spent hours looking at logic analyser output, scope traces, and software dumps searching for clues as to what had happened to cause the failure that I was debugging.

The same problem occurs with modern electronic systems. As automotive manufacturers look for greater reliability, we are looking at how we can prevent failures in the parts-per-billion range. What chance do we realistically have of ever witnessing a failure that occurs at a 1 ppb rate?

The answer is simple. The designer has to build systems into the car that perform self test and error logging functions that leave the vital trail of clues to help identify any problem. A good example of such as system are the batteries in a hybrid or electric vehicle. To get the most out of the battery, a great deal of data needs to be collected and processed including charge cycles, charge rates, temperature while charging and discharging, etc. If the manufacturer provides a 5-year warranty on the batteries, they will need to know that during the entire life of the battery, that it has not been mistreated. If it has, they will need to implement fixes to prevent the failure from happening again. Cue the need for a data log.

One key element of the data log is that it must be nonvolatile (so the data is preserved when the battery fails) and it helps if it can be written quickly and as often as possible. It’s no surprise then that F-RAM has been chosen in some of these applications. It has virtually unlimited endurance and its fast write allows designers the option of writing data continuously until a failure occurs. The F-RAM will then contain a short record of the operation that contains the trail of clues that would even impress Sherlock Homes!