This thread is really interesting as it discusses component ratings. I come from a background where components used in mission critical applications were heavily over engineered. Even when a component had a rating of X Volts, it was a pessimistic value and the components would often have better capability, it was just not guaranteed. We often tested components to destruction and were impressed with the true headroom on a component rather than that indicated by the data sheet. Whilst it is true that it would be unwise to deliberately run a component beyond its maximum ratings in an important role, it might not be such an issue to run it at or near that rating if the manufacturer has already calculated a decent margin of safety to cover issues like transients. If transients are considered a risk them maybe a TVS can be used in the supply to the chip ? In important applications, some decent supply filtering and transient suppression is wise anyway.
If I were in Mike’s position I would sacrifice a few of the chips in a torture test to see at what voltage they fail and the failure mode. Such is useful information anyway as a non safe failure mode would either steer me away from a component or cause me to employ additional safety measures that might otherwise have not been required.
When there is little choice of components for a task, it is sometimes worth a little experimentation to see just what can be used safely without breaking the bank or having to completely change a design. This is, after all, what OEM’s do when prototyping, often to test reliability, but also to see how cheaply a design can be built and still meet the needs of the customer. Those who get it wrong do cause issues with premature component failures though.
Fraser