At 12:45 PM 4/29/00 -0600, Dan Michaels wrote:
>Tom Handley wrote:
>>   Dan, Robert has provided a summary. It boils down to basic engineering.
>>Know your environment and know the device characteristics. I have'nt had
>>a Tantalum cap fail in decades. There is a good reason they are specified
>>in vendor's application notes. If you use a 6V Tantalum in a 5V supply of
>>questionable design, you are asking for trouble.
>....
>
>
>Tom, is it possible your circuits have all luckily fallen onto
>the good side of the "border" that Robert was talking about?
>Ie, power supplies with effective series impedance somewhat
>larger than 1 ohm?

   Dan, I'd like to think it was attributed to good design ;-) I just pay
close attention to vendor data sheets and try to `bullet-proof' the design
by looking at the environment. Most of my experience is in process control.
I have blown Tants but it was due to `stupid human tricks' during prototyping
that we've been discussing in another topic. Even in a 5V logic environment
with a linear supply, I specify 16V caps.

   - Tom

>BTW, for another "rule of thumb", I was going to mention
>that I measured the series R in a number of wall warts a
>couple of years ago, and they were all pretty substantial,
>10 ohm range or greater, for the smaller WWs.
>
>For instance, the difference between Vopen_circuit and Vloaded
>was generally 3-5v. Worst cases would be the larger WWs. Say,
>[Voc-Vloaded]/Ioad = 3v/1A = 3 ohms, close to Robert's border.
>Smaller WWs have higher R.
>
>Cheers,
>- Dan Michaels

------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)