Electronic – How to break components in SPICE

componentsfailureltspicemaximum-ratingsspice

I've been learning SPICE over the past few days, using the LTSPICE program. One thing that just escapes me, is how exactly do we know when a component's absolute maximum ratings have been exceeded? For example, the diodes have a maximum current flow, however, no matter what I set it to, it always simply works. Even when the design is blatantly violating the ratings.

This brings 2 questions:

  1. Is there any way to enable something that lets you know when some component's maximum ratings have been exceeded?
  2. If this doesn't exist, what is the purpose of inputting the maximum ratings into the component's model?

Best Answer

Most SPICE simulators have the ability to monitor operational regimes, telling you when a transistor is in sub-threshold, triode or full active and likewise for current density and over-voltage. If you don't have this in your simpler models you can easily put together macro-models that wrap current monitoring and voltage levels around the device using ideal elements. Of course you can also use .WATCH which aborts the run if parameters are exceeded (using max and mins) and then there is .WCASE which is pretty complex so I'd get my hands dirty in other areas first. Of course you can also run .MC (Monte Carlo) too.