If it cannot be used for a power supply input that needs surge protection, but it could be used for something else, and we are talking about protecting a power supply input, then how exactly is it different from what wrote?
Have you looked at the devices that are mentioned in that vishay appnote? They are not regular TVS diodes, they clearly have some sort of MOV or other device integrated into them, and are called "TVS devices". I mean, yeah, if someone names their MOV a TVS diode, and then that makes me technically wrong, congratulations, here is one internet point for proving me wrong: 1 
They... they give part numbers?
e.g.
https://www.vishay.com/docs/88382/sm5s.pdfIt's a diode.
They don't
say what it's made of, but "passivated junction" doesn't make much sense outside of planar semiconductors, and given the voltages, and
as it was the style at the time, it's certainly silicon based.
At worst, it's a diode in parallel with something, but absolutely nothing else but an avalanche diode will give you a 39V Vpp at 93A while also breaking down at 28V (5mA).
They give waveforms too, and clearly the peak voltages are in line with the datasheet.
They mention "EPI PAR" (and non-) types, without defining what those mean. And in fact PAR seems to only appear in this article, its alternative forms, and the product line itself. I'm guessing it's "passivated anisotropic rectifier", but they don't actually show the abbreviation side-by-side. Shoddy notation.
Now, there are plenty of boners to critique in the application note -- it is as notoriously bad as any other appnote -- but,
the ways in which it is bad are more interesting than simply stating it's bad. I mean, they're all bad, that's kinda the starting point.
...
...Aha, this is probably the patent:
https://patents.google.com/patent/US5399901They must mean "anisotropic" as in part of the fab process, i.e. using KOH etch to make a pyramidal depression. Which is done to expose the edge of a depletion region, forming a mesa, which is then passivated (presumably with SiO2, hence "glass passivated"). I assume because the mesa can have more even current density / freedom from defects, and perhaps guard rings and surface states weren't well enough understood at the time (but I mean, this was the 80s, HV MOS was already well under production; maybe as a largely(??) bipolar/rectifier company they didn't have much knowledge/tech on those topics, who knows?), and this was done to make cheap robust rectifiers with reasonable avalanche ratings, indeed including load dump ratings. Probably modern Vishay parts are similar, though they could just be your average modern planar epitaxy something or other.
Oh, and epi vs. non would just be how the PN junction is formed, epitaxy or diffusion, evidently the latter having higher internal resistance or built-in potential, whatever the case is.
Anyway, I don't see where you get an MOV feel from this, or why it should be anything other than what it says it is.
Again, we can formally critique the appnote if we like, but this extreme conclusion doesn't seem supportable in any way.
As stated earlier but not explicitly, a 150 A 8/20 µs TVS can be used on a supply line if other components on the power supply line dissipate or smear out some part of the energy, which is more often than not the case. One small is enough to reduce the peak current trough the TVS. Of course the TVS on it's own will just go up in smoke.
Again,
what power line?
If in present context, then OP never specified load dump parameters (peak voltage, duration, impedance), so at best all we can do is say whether it could work at all (which, I think is safe to conclude not; I'd be shocked if the survived even 12V load dump). Whether any particular level, who knows.
And, load dump is slow enough that reactive components do little if anything, at least at realistic values; that said, maybe someone wishes to put one of those automotive amplifier "boost" capacitors in there, a couple/fraction of a farad across the line, which would do the job, actually surprisingly well; but for production purposes, that'd be an odd pick at least. (But an interesting one to see in a real product, hah.)
If you're still stuck on IEC 61000-4-5 surge and 150A "not existing" in that standard, then, perhaps; but, again, there are numerous applications of that standard where the peak current is significantly reduced, so it's perfectly reasonable that a small device can handle something like that.
I don't think there are MOV's in there because MOV's deteriorate on every surge event. Those are probably zeners with very descent heat slug at least the package looks like that.
MOV manufacturers give curves for infinite lifetime. Only undersized MOVs, or excessive surge conditions, cause significant deterioration.
Tim
Home
Help
Search
Login
Register
