wiederling at googlemail.com
Fri Aug 29 18:32:31 CEST 2008
On 8/29/08, Joerg Reisenweber <joerg at openmoko.org> wrote:
> Nope, Tranzorb won't help here because the energy this component had to absorb
> is too high, so it would burn out. Transzorbs are for ESD surge suppression
Yes, but the trick is that they burn to a short circuit. You still need a fuse
element in front that burns garanteed open ( fuse, resistor )
Design target is to aim for a reasonable repair and avoid a fullbrick.
> However meanwhile main rant here seems to be about additional cost for a
> ~$0.05 diode to clamp reverse voltage and trip the polyfuse we have in new
> GTA03 design. Obviously there is a notion customer wouldn't like to pay this
> price for increased ruggedness of USB-power input. Also there have been
> objections about the safety of such a design, not taking in account that it
> can not be less safe than what we had originally.
same applies here if you use the unsymmetric variety.
Overvoltage and reverse voltage draw current through the TransZorp
long enough to have the fuse blow. Save!
A freerunner is more of a cherished posession than forex a Motorola F3 ;-)
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