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'[PIC]: Can standard 16F628 operate below 0 centigr'
2002\03\19@142325 by Gary

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Hi,

PIC16F628-04/P running at 4Mhz @ 3V


I have designed a project using the PIC16F628-04/P, microchip states that the operating temperature is 0c to +70c, how low have you run this chip at successfully.

I realise you can get different versions for lower temperatures, but I am interested how close you have to be to the tolerance in the book?

This is going into a commercial device, so I assume we may well have to go for the 'lower temperature version' ?

Any idea on the difference in price between PIC16F628-04/P, PIC16F628-04I/P, PIC16F628-04E/P versions.

Thanks Gary

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2002\03\19@151652 by Douglas Butler

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In my experience with running uPs cold, the problem is that the port pin
drive goes out of spec, then the oscillator stops (or won't start).  If
you lightly load the ports, and use an external oscillator or a crystal
brand you trust, you may be able to bend the rules significantly.  I
have never used the 16F628 so you will have to run tests yourself.

Sherpa Doug

> {Original Message removed}

2002\03\19@152312 by Eisermann, Phil [Ridg/CO]

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The short answer is ..... You can safely run it down to ZERO decgrees
centigrade.

Some standard grade chips will work below zero, some won't. There is no
guarantee how much lower *all* chips will run at. It's similar to the
overclocking debates. Some chips will run with faster crystals, some won't.

Since this is a comercial device, you were given (or proposed them yourself
for someone to approve). Get the chip that meets the specs.

Now, having said that, I've run a standard grade 16C711 chip to almost -40
centigrade, at which point it stopped working. This was the only chip that
made it that far. Another micro made it to -20. These were '711 devices made
by an outside design firm that doesn't know how to read a spec sheet: the
product was required to work +60/-20 centigrade. Why they used standard
temperature chips is beyond me. Lots of stuff started deviating (op-amp and
pressure sensor) or malfunctioning (micro and serial interface) around -15
to -20; it was hard to tell if it was the micro or other components. The
exercise of finding out really wasn't worth anyone's time.

Bottom line is that specs exist for a reason. If your product fails because
you exceeded the mfg. specs, you have only yourself to blame :)

Oh, and let me get this off my chest as well -> ignore all the specs on a
datasheet marked 'typical'. That's useless marketing information. Ok, now i
feel better :)

Anyone have differing experiences they'd like to share?

--
Phil Eisermann


> {Original Message removed}

2002\03\19@160357 by Jinx

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I've tested a commercial-grade F84 to -15C, but not with
regard to start-up. It runs OK, although you will find that
WDT and IntOsc (F628) will get slower. It's easy enough to
check, just pop it in the freezer in a plastic bag

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2002\03\19@181014 by Sean Alcorn - Avion Sydney
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on 20/3/02 6:18 AM, Gary at spam_OUTquestuk1TakeThisOuTspamHOTMAIL.COM wrote:

Gary,

> Any idea on the difference in price between PIC16F628-04/P, PIC16F628-04I/P,
> PIC16F628-04E/P versions.

We ONLY use extended temperature versions. They are not that much more
expensive. Maybe a 10% jump from "Standard" temp to "Industrial" temp and
then another 5~10% from "Industrial" to extended.

The trick is that you will very rarely find stock (or at least we don't in
the Asia Pacific area) so you are looking at 4 weeks lead time on average.

If you are going to operate at or below zero, I wouldn't push it.

Cheers,

Sean

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2002\03\20@140042 by Peter L. Peres

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>I've tested a commercial-grade F84 to -15C, but not with
>regard to start-up. It runs OK, although you will find that
>WDT and IntOsc (F628) will get slower. It's easy enough to
>check, just pop it in the freezer in a plastic bag

I've tested several PICs down to (unmeasured, theoretical) -55C
(electronic freeze spray until it pools on part) with no bad effects. I
did not see any one of them 'stop', until condensation reached the osc
pins. The PICs were 16F84 (not A) and 16C54 CERDIP (not A). I also froze
12C508A OTPs on internal RC clock but their clock deviation prevented the
circuit from working a long time before -55C was reached (for causes other
than cold - the timing went bad). I did not test oscillator startup when
cold on any of these parts, but I know that there will be problems with
that. The circuits were started at room temperature and then heated and
frozen alternately a few times.

I believe that a PIC run with external rail to rail clock and no analog
sections used in it should not stop working down to -55C. Maybe the 711
copes better with the deviant environment because its analog sections
force the manufacturer to pay special attention to masking etc and the
logic threshold levels must be about perfect as a side effect.

Peter

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2002\03\21@041115 by Vasile Surducan

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On Wed, 20 Mar 2002, Peter L. Peres wrote:

>
> I've tested several PICs down to (unmeasured, theoretical) -55C
> (electronic freeze spray until it pools on part) with no bad effects. I
> did not see any one of them 'stop', until condensation reached the osc
> pins. The PICs were 16F84 (not A) and 16C54 CERDIP (not A). I also froze
> 12C508A OTPs on internal RC clock but their clock deviation prevented the
> circuit from working a long time before -55C was reached (for causes other
> than cold - the timing went bad). I did not test oscillator startup when
> cold on any of these parts, but I know that there will be problems with
> that. The circuits were started at room temperature and then heated and
> frozen alternately a few times.
>
 Could you tell us what's happening between +5...+10C ( long time
test ) after a frozing cycle ? How the humidity influenced your measurements ?
Thanks, Vasile

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2002\03\22@021433 by Peter L. Peres

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> what happens between 5 and 10C when thawing

As I said humidity affects the PIC, especially the osc pins. I did not do
long term testing, I tried to simulate the effect of a rapid climatic test
run on the bench. If condensation on the PIC is what troubles you just
scrub the PIC and board squeaky clean (acetone etc) and apply conformal
coating everywhere where it will not infere with circuit operation (and
*cure* the coating as per manufacturer's specs).  Refined (!) beeswax is a
useful conformal coating if you are poor or otherwise limited in choices,
and limited in temperature to +50C or so.

Peter

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