Franc Zabkar wrote in message
...
On Mon, 11 Jan 2010 08:25:42 -0000, "N_Cook" put
finger to keyboard and composed:

But,unlike zeners , are they guaranteed to go short circuit if they end
up
in what becomes a sustained overvoltage rather than just a transient
situation ? or 2 different clases of TVS ?

I watch various hard drive forums. HDs nowadays use TVS diodes on
their +5V and +12V rails. A sustained overvoltage from, say, a 19V
laptop adapter always (?) shorts the 12V diode, unless it is protected
by a fusible zero-ohm resistor.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

A zener would normally burn up/ go open circuit in overvoltage but do VTS
normally (but not guaranteed) go short thus providing crowbar protection if
fuse/fusible R/ current limiting/ps shut down, upstream. 80 percent/90
percent/ 99 percent of the time go s/c rather than o/c , any
guesses/knowlege?