| Electronics > Projects, Designs, and Technical Stuff |
| Is "integrated circuit burn-in" a thing? |
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| IDEngineer:
--- Quote from: SiliconWizard on April 25, 2019, 02:07:13 pm ---In your case, I'd venture there is probably something very wrong that is way beyond the scope of burn-in. Failures in a matter of a couple hours in normal conditions with several devices doesn't look right. So either the batch of ICs you got is all faulty, or your design is? --- End quote --- The evidence is mounting that this is an ST problem. I'm up to ~72 continuous hours on some BMI160's with zero issues (just scoped them again before typing this). That's the exact same PCB, exact same BOM, assembled at the same time as the LSM6DS3 boards, same same same EXCEPT for which part was stuffed in that footprint. As noted earlier in this thread, those two devices happen to share a compatible footprint so we can build boards that are identical in every way except for which device is stuffed into location U7. The LSM demonstrates this weird "burn in" behavior, while the BMI appears not to. --- Quote ---You should probably contact ST for support. --- End quote --- :-DD :-DD :-DD |O |O |O See my comments about ST support earlier in this thread.... :rant: :horse: |
| IDEngineer:
I've just remembered one "difference" between the two devices: Their "typical" supply voltage. The LSM has supply specs of 1.71V (min), 1.8V (typ), 3.6V (max). The BMI has supply specs of 1.71V (min), 3.0V (typ), and 3.6V (max). We run both parts on a 2V5 rail that was already in this board's previous design. I personally contacted both vendors and asked them if their 1V8/3V0 was actually preferred, or if 2V5 (which is obviously well within both device's specs) had any disadvantages compared to their "typical" supply voltage value. Both companies replied and explicitly said that 2V5 was perfectly fine and that voltage had no disadvantage compared to the "typical" values they listed in their spec sheets. I don't think that could cause this LSM problem, but I did notice it and got the manufacturer's opinion before committing. That said, 2V5 isn't their "typical" value for either part and is 50% higher than the LSM's "typical" while still comfortably within its acceptable range. Just tossing that out there in case it rings a bell for anyone. Again, I can't imagine how a part would stop locking up after it "grew accustomed" to a different supply voltage.... :o |
| IDEngineer:
--- Quote from: m98 on April 25, 2019, 08:06:50 am ---I was just about to design an ST accelerometer into a product. Guess I will use an alternative part instead. --- End quote --- The Bosch-Sensortec BMI160 (compatible footprint, though not firmware compatible) is looking good electrically. However, it appears less tight on its axes-to-package physical alignment. I'm seeing misalignments of 2+ degrees on some BMI160's. Your downstream firmware can compensate for this by doing the appropriate 3D coordinate rotations, but it's something to keep in mind. Some earlier MEMS devices included guaranteed specs for the alignment of their die axes with those of the package. I've noticed that particular spec has disappeared from most spec sheets now. My guess is it reduces production cost for them by not having to individually characterize every device, and they probably assume most installations are doing some sort of in-place calibration anyway so why duplicate that. The downside is that with these earlier devices their alignment was often close enough for many non-critical applications as long as your pick-and-place equipment did a good job, but now it appears you cannot rely on that unless +/-2 degrees of misalignment doesn't matter. Maybe it doesn't for game controllers or something, but in our case it DEFINITELY matters. This had me originally favoring the LSM but given that part's apparent reliability issues the BMI is looking better every day! |
| SilverSolder:
Could it be that you were just unlucky, and if you bought some more parts they would behave better? |
| jmelson:
--- Quote from: IDEngineer on April 25, 2019, 03:09:53 pm ---The evidence is mounting that this is an ST problem. I'm up to ~72 continuous hours on some BMI160's with zero issues (just scoped them again before typing this). --- End quote --- Do ALL ST devices go through this issue? If so, I'd suggest getting a few new units and hand-soldering new parts on your boards and repeat the test. It may be that the stresses of reflow soldering in their process may be exceeding what the chips can handle. If you can hand-solder the ST parts in and they are fine, it has to be something to do with the soldering process (or maybe even the P&P machine is shocking the part when planting it on the PCB.) Jon |
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