[sdiy] can a PSU destroy voices chips?

Neil Johnson neil.johnson71 at gmail.com
Tue Nov 19 17:50:56 CET 2013


Hi,

On 19 November 2013 16:43, Jean-Pierre Desrochers <jpdesroc at oricom.ca> wrote:
> Sometimes supply regulators in/out pins can get shorted (inside)
> and cause a too high level at their output pin.
> I saw 7805 regulators going bad outputing there VDC input
> (for ex 8-12vdc) at the output pin causing chain reaction...
> IC's destroyed..

Except in this case the problem was the positive supply going to 0.
NOT going above nominal.

> The solution... I'm about to try it..
> just put a transorb in parallel with the regulators output pin
> to keep the voltage from going above a certain level.
> Like a 17.1 volts breakdown 1.5KE18AG at the output
> of a LM7815.

Carefully read the datasheet of that device.  The 17.1V is the maximum
working voltage.  The clamp voltage for that device is 25.2 volts.

Neil
--
http://www.njohnson.co.uk



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