Hi all,

Speaking of radiation and it's action on devices.  I just noticed in the
LP2981 data sheet (low voltage regulator) that sunlight or even halogen
lights can cause misbehaviour.  Since this is an SOT23-5 device it
follows that the plastic over the die isn't opaque enough to keep the
chip in the dark.

John Dammeyer


> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Alan B. Pearce
> Sent: Wednesday, April 24, 2002 4:20 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]: Xrays and Flash memory
>
>
> >I had a girlfriend who is a doctor in a vet clinic. So I
> made up a test
> >card of EPROMs and EEPROMs, in two batches.
> >She then exposed them to the X-rays, the first batch for
> about 10 secs,
> >the second four times that.
> >I wanted to get maybe a second life out of the big number of
> OTP parts
> >that are around...
> >
> >But sorry, no go, the intensity was WAY too low, and as it was in a
> >clinic I am inlcined to say that YES, it would have stained a film...
>
> X-rays will eventually erase EPROM's.
> I remember a story related by someone presenting a paper at a
> conference. He
> worked in a university that had a medical section, and was
> asked to build a
> dummy patient that could be used by students when training on a x-ray
> machine so they could see the motion of organs. This machine
> must have been
> capable of continuous display.
>
> Everything worked well for a while, but then intermittently
> the dummy body
> would give an involuntary twitch, with intervals between
> twitches getting
> shorter until the dummy body went into total spasm. The x-ray
> machine had
> erased the EPROM's used. In this situation the solution was to move to
> bipolar fusible link proms that were pin compatible.
>
> As a side issue to this, in the space electronics environment
> where I now
> work, we use small pieces of tantalum sheet glued and tied
> over the top and
> bottom of components that do not have sufficient radiation
> capability for
> earth orbit flight. One of my colleagues recently did this
> for some EEPROMS
> used on a low earth orbit instrument he was working on. Tantalum is
> apparently one of the highest density metals when it comes to stopping
> radiation, presumably on a weight/radiation stopping
> trade-offs, but that is
> not my area of expertise.
>
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>
>

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