At 12:29 AM 1/31/2006 -0200, you wrote:
>I've just had a quick power shortage at my house... Ligthning, then the
>lights went off for a second and back on again. Only problem is the
>PIC18F4525 I was working with is no more. ICD2 reports its device id as 00,
>I can program it but it fails. Other chips in the board, including CMOS
>logic, CMOS op amps and a VFD display were not harmed.
>
>That's actually the second pic I have that burned in this fashion, the first
>went away when a short circuit in the AC part of the circuit board
>presumably caused a power surge. And again the PIC was the only component to
>fail. A previous board version had problems with relay switching resetting
>the pic.
>
>Now, these are hand built prototype boards for a product I expect to have
>ready in a month or so. It's a low volume production (20 units per year or
>so) but a quite expensive product and it would look bad if customers had to
>replace control units every couple months... This is actually my first pic
>product so I figure I'm missing something here.
>
>The power supply consists of a transformer, full wave rectifier with 1000uF
>electrolytic, a 7805, another 1000uF electrolytic with a 100n disc cap, and
>every digital chip has its own 100n disc cap. Board current comsumption is
>in the 400mA range. Would a series inductor help with the problem? What else
>can I do to make my project surge-proof?
>
>Thanks in advance.

You problem might be more to do with I/O than with the power supply. It could
be the circuit design or the layout. But, no, PICs are quite robust
generally. Your earlier noise problem suggests strongly that you have layout
or EMC design issues in general.

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


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