[s-cars] Engine stopping problem -- Starting Issue

[Paul Gailus]

I agree with James's comments.
10 years has become a defacto industry standard for
data retention in EPROMs and many other non-volatile
memories.

IC manufacturers predict expected lifetimes under
"normal" conditions by extrapolating from the results
of accelerated life testing at elevated temperatures.
They have typically extrapolated using an assumed
"Arrhenius law" for time to failure vs. temperature.
But I've seen recent papers indicating that this failure
model may be significantly overestimating the data
retention time that will actually be achieved under
normal conditions.

On the other hand, I doubt that this has had much
effect on the specs quoted by EPROM manufacturers.
For one thing, they've typically been very conservative
on their numbers in the past. In fact, I've heard that some
didn't want to quote lifetimes longer than ten years
because they thought customers might think they
were paying for overspec'ed parts and go elsewhere.

I do have a specsheet for an automotive temperature
range version of the 87C257 EPROM, but it doesn't
include any data retention lifetime specs.

The botom line is that I'm not losing any sleep on this
one. Although maybe I should take another look
at those control arms ;-).

Paul

----- Original Message -----
From: James Murray (LMC) <James.Murray at ericsson.ca>
To: <thomas.pollock at AMD.com>; <miikka.salonen at kolumbus.fi>;
<s-car-list at audifans.com>
Sent: Tuesday, May 06, 2003 4:50 PM
Subject: RE: [s-cars] Engine stopping problem -- Starting Issue


Most datasheets for most EPROMs specify a minimum 10 years of guaranteed
programming lifetime, however several factors can shorten the life of the
data programmed onto an EPROM. Exposure to heat and ultraviolet light will
decrease the life of an EPROM. A well cared for (or, at least non-abused)
can last upwards of 25 years, so I would say we all have many years to go!.
I've never checked the spec's for our EPROMS, perhaps someone can chime in?
I'll bet they are good for a much longer than 10 years...

/J.

-----Original Message-----
From: thomas.pollock at AMD.com [mailto:thomas.pollock at AMD.com]
Sent: Tuesday, May 06, 2003 10:31 AM
To: miikka.salonen at kolumbus.fi; s-car-list at audifans.com
Subject: RE: [s-cars] Engine stopping problem -- Starting Issue


Any electrical engineers out there ?  6 years ago is a long time.  I don't
want to start a panic but all electrical components have a life span. The
flash parts that hold the software in our ECUs definitely have been spec'd
for how long they will hold up before transistors break down etc. Oh, and
the more you reprogram them the quicker they start to break down. I don't
have a data sheet in front of me but I wouldn't be surprised if they are
spec'd for "maybe" ten years or so. That wouldn't mean that in ten years we
all suddenly start failing but...

Now depending what kind of application a certain part is being designed for
(military versus commercial etc) and how much room is left in the flash part
to put "extra" code in, you can do all kinds of things to check and in some
cases repair circuitry that is on the way out. I'm not at all familiar with
the software side either so who knows...  Anyone ?

tom.