Why not integrate Jaguars with Diodes?

[Matt Krass]

Originally Posted by EricVanWyk

That is a pretty diode! I just wish it was smaller than a spike

Compare figure 3 of that diode's datasheet against the figure on the 40Amp circuit breaker's datasheet. A 400Amp surge would blow the breaker in 30 to 60 milliseconds, and is on the edge of what the diode can handle.

For even more fun, take a look at the 120A circuit breaker's datasheet. At 600 Amps, it guarantees to blow within 3 seconds.

Well, this may not be the perfect diode for the job, but I assure it was selected through a very rigorous "what can I get my hands on in the next five minutes" selection process. Also, if you were to parallel the two diodes per package it would give you some fairly substantial breathing room on those figures. If I get a chance soon I'd like to put my storage 'scope on the diode and capture the waveform and see exactly how effective it is.

Also, as I mentioned before, I'm not sure that the Jaguars failing is any gentler on the system, and I'm sure the components failing in that aren't nearly as good at handling the surging currents safely, I'm still feeling as if I'm in the lesser of two evils camp here. I concede this is mostly a hunch, after looking over the Jaguar schematic I suspect the failure mode is near a dead short in one of the logic regulators. I'm not sure that the opportunity to get hard data on the Jag failure is going to present itself anytime soon (I think my team would be a little unhappy if I sacrificed one of our remaining Jags to the cause ) though I am unsure if the blown out ones have all been disposed of yet.

What are your thoughts on the risk of the failing Jaguar blowing the breaker over and over vs a properly heatsinked crowbar diode (or two in parallel) rated for the actual load?

Matt