Flash retention in uC at higher temps, experience?

I only have some small experience here with the MSP430. It seems to operate at 140C at 3V and 3.3V for the several-hour long tests I've done. But some bad experiences in storing data into the flash at that temp and even at 3.3V and higher. But I didn't need the darn thing to survive all that long, either.

I haven't read, for understanding, the data sheet you mentioned. I just downloaded it, though, and thanks for pointing it up. I think it wasn't around when I looked a few years back and I'm glad that you pointed it up for me.

Your obvious solution is to move north about a thousand miles. ;)

Jon

Our boxes never see direct sun exposure on the semis, but they're encased in an aluminium box, then in a black plastic 'pelican' waterproof case. Here in Australia, it gets quite warmish over summer, and we routinely see the insides at 50C (122F) or more (as far as the measurement of the internal temp sensor goes anyway).

Our flash chips are quite ancient, and although they don't hold any critical information, it's critical enough that you're going to notice if it chucks a wobbly.

Although we get some with corrupt flash data, it's relatively rare.

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One of my clients makes products that regularly go above 80C, and that has never been an issue to my knowledge (all the service guys I used to hang with have either left or been promoted, so I don't have that immediate knowledge one gets by being service's life line). Certainly the to-do if it were recognized would have bubbled down to me.

OTOH, all the parts are very carefully selected to work over the industrial temperature range; if your mailbox thingie is designed with commercial temp range parts all bets are off (and it may be something else that's happening, too).

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Wow, problems within hours at 140C? Not cool :-(

My wife would absolutely not do that.

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50C is easy, we even get that as an ambient temperature around here. But in summer stuff inside of enclosures can easily reach 80C or more. Worst case for 10h/day all summer.

Chucks a wobbly, cool. Learned a new expression!

Depends on what "relatively rare" means ;-)

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Well, in my case it kind of has bubbled down to me now ;-)

It's not just this mailbox but also some MSP430 apps at a client. They predate my involvement there and we are pretty much stuck with that for a while. We are seeing a distinct pattern where those inside smaller boxes fail more often than those in larger and more airy enclosures. This stuff is used in the south where summers are quite toasty.

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Have you tried cooking them on purpose? Even if you don't have a "real" environmental chamber, you can do a lot with an insulated box and a heat gun (including catching the lab on fire (ask me how I know!), but that usually entertains the technicians).

I'd toss some in an oven for an extended high-temperature test, to see where they failed.

I'd also check the heat rise against ambient in both small and large enclosures.

If they get any solar load, I'd throw up my hands and call a mechanical engineer who's good with thermodynamics, but that's just because I (usually) know where my competence ends.

Some of the flash parts that I have seen used to success have been from TI, but they aren't TMS430s, and they _are_ industrial temperature range parts.

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Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

That I haven't tried yet. A friend of mine (chemical engineer) did something similar. After an extended hospital stay he casually mentioned that his lab was now a black hole and that the door was gone.

That's what I suggested to the client, to place some USB temp loggers in there.

I wish the MSP430 was available in automotive but it ain't. At least not according to the TI rep.

One could add some code so it re-flashes itself once in a while, that's another option here. However, the device cannot lose power during that brief period or it'll be really toast. So that would require large enough electrolytics and some pre-regulator voltage monitoring. The latter would require a relayout, bigger ECO and all that. Not a VP of Engineering's favorite path, usually.

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What do you mean by strong? VHF radio close by? Cell phone? If yes, do you remember how close?

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I have found strong R.F. and EMF's in close proximity have caused the flash to get corrupted in PIC's. I'm sure it effects others.

"

100 W VHF transmitter ~ 6 feet away.

Another problem I have heard of but never experienced and that is police microwave radar. I guess for some uC's there are circuit paths that match the wave length and can cause unwanted effects in the memory.

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For more critical uses, Infineon seem to have well-spec'd uC - their new ones all have Error Correcting Flash, and 125'C models.

Also recently added are a series of Transmitter ICs for Wireless Control, that have Sub 1GHz Transmitters, and Low power Flash C51's

- one targets Tire Pressure, at Automotive temp range.

Flash retention is one of those 'fingers crossed' specs from most suppliers. They cannot TEST years of use, so they do a little extrapolation, and we all know, extrapolation is dangerous :)

From What ?

-jg

I was going to suggest that. But, you ask, "How often?"

A few wild troubleshooting ideas:

One thing you might do is vary the device's Vdd while reading it, thus changing the read threshold and alerting you to marginal cells before they fail.

With a heat gun and a device reader you might actually document the bleed-down of the device's memory cells vs: temperature & derive a definitive lifetime projection.

Another idea: can you control the programming timing? If so, you could weakly program a test pattern + CRC in the part. The part could then test the area itself, detecting impending failures.

Cheers, James Arthur

No. No problems, at all. Just that I didn't run them for more than about 5 hours at a time. Same one ran for weeks, though, at periodic elevated temperatures. I was just collecting data from a rotating hot surface and wanted to just stick the whole contraption there while it stored a few bits of data into RAM. The battery was the problem.

Oregon is absolutely beautiful! I've got pileated woodpeckers, 4 kinds of squirrels including a flying squirrel (nocturnal), peafowl, chickens, guinea hens, turkeys and so on -- tall 60-80 year old firs, two kinds of ferns, rhododendrons that bloom in succession around the place, and it looks like a lush rain-forest national forest when you walk the paths on the property. Lots of acres, 5000 sq ft home, 1/4 mile driveway to the house, view of the mountains, 5 minutes to a hospital and 20 minutes to the PDX international airport, a 17 mile well-maintained walking and horse trail that goes from 1/2 mile away from my home to the Willamette River in Portland, and it cost me $330k in 2002. Prices are still low, too. Next door has been on the block for 2 years, is a million dollar home (tax appraisal price) with about

4500 sq ft and 5 acres, and is being offered at $599k now. I'm told they'd accept under $500k. Neighbors are wonderful, too. 3' of fantastic soils, 45" of rain a year nice and evenly distributed all year 'round in a constant drizzle, and everything grows where you throw the seed, no digging needed. What could be better? ;)

Jon

In a high radiation environment usually some ECC bits are stored in each sector and with frequent sector reads you can detect if there are flipped bits, correct the errors using the ECC and write back the sector.

In this way, you know when to do the writeback and you can minimize the (limited) number of reflashing for a specific sector on the flash.

I assume this would also work with the data retention time problem at elevated temperatures.

For a program written in assembly, it should not be a problem to allocate a number of bytes for the ECC bits at the end of sector and use a branch instruction to skip them, but this might be an issue, if an HLL is used.

Paul

[...]

Sounds great if you want to become a farmer :-) I'm living near Cologne centre, but a quiet back road near the Rhein. Just a rented flat and not acres of grass and bushes around it, but supermarkets, stores, pubs, restaurants, theaters, cinemas, parks etc., all within walking distance.

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If the flash is big enough, you could copy the program to an unused memory area and back again the next cycle. Then the only critial moment is writing the switchover. But should be no problem, if you can monitor the supply voltage and if you can guarantee, that it remains over the flash limit for the time needed to write the switchover bytes.

What do you think of MRAM for critial applications? It's a bit expensive, but they claim data retention of minimum 20 years and unlimited number of writes. It is even used in a satellite:

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You can collect all ECC bits at the end of the flash.

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For us, it was a non-issue above 40C, because we didn't rate the measurement electronics to be within specification above that point. We actually could have gone higher, but the built-in LCD 1x16 display wasn't rated above 40. It was a nice round number so we left it at that.

It's an oldish Australian term. I don't know how wide spread it is, but everyone here who I've mentioned it to knows what it implies.

Of the dozen or so broken boxes I used to see every week, we'd get one with trashed flash data every month or so. I have no idea how many boxes were in service in the outside world. I'm guessing many hundreds, but I really have no idea as I was only involved in the service side, not sales or other areas that would give me an idea of what was already sold.

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