Depends, Mil parts are standard 125C ambient (to meet spec) so most parts can handle this without failure. We do have that 210C part and the xDSL drivers have an extended range to 150C.
Practically 125C is probably OK forever on die temp without any issues other than JFET gate currents being nA rather than pA. You also must take into account the plastic transition point of the package, if applicable.
You would probably have to get the information for each chip then use something like relex reliability software:
Relex Reliability Software - General Information
And calculate your MTBF figures etc, I don't think there is a global defined industry standard.
As Bonsai mentioned, automotive is the new high reliability, harsh environment for a lot of devices especially since the Toyota incidents. We do layouts for ECUs etc and they are quite stringent in their requirements and rules for safety, such as every MLCC cap doubled up when used across power lines.
Relex Reliability Software - General Information
And calculate your MTBF figures etc, I don't think there is a global defined industry standard.
As Bonsai mentioned, automotive is the new high reliability, harsh environment for a lot of devices especially since the Toyota incidents. We do layouts for ECUs etc and they are quite stringent in their requirements and rules for safety, such as every MLCC cap doubled up when used across power lines.
WHAT?? The Toyota incidents have NOTHING to do with normal safety and MTBF science.
It's a consequence of political foisting of ROHS. Knee jerk adoption of a standard which forces the entire world to use horribly unreliable technology. Whiskers were well known decades prior, yet nobody cared.
jn
I am on about doing automotive layouts, different paragraph than the first one and not related to the MTBF comment. Since the Toyota problems doing automotive designs has become almost as stringent as doing aerospace, they are frightened of something else going wrong and get a first class lawsuit thrown at them. I did miss a full stop out re-reading my comment, which probably confused the issue.....
Will go sit in the corner now in disgrace
As to RoHS, I wont comment, I was very active in the early days trying with many others to get people to see sense, but where politicians are involved, common sense truth and integrity seem somewhat missing, the lead in electronics was miniscule and was put in the misc 1% of lead uses when all the information was being put out to convince us that we were all being poisoned. The only way to stop whiskers reliably is 3%+ lead mixed with the tin.....
Last edited:
Nasa did an analysis of the Toyota thing. Turned out a connector was tin plated, and whiskers shorted connections, and caused the software package to enter a state where the unintended acceleration occurred.
In the solder thread, a link was provided to a nasa ppt, page 57 on discussed the Toyota incident. I'll go get the link and put it here, wait a sec.
I'm back.
Courtesy of phaselag (paul)
http://nepp.nasa.gov/whisker/reference/tech_papers/2011-kostic-pb-free.pdf
jn
From the article it appears that this issue was never a real concern. The equivalent of a few lead acid batteries at best for the entire industry. The fume inhalation is nil and the ground water contamination was shown to be overstated at best. Why the industries could not counter the arguments put up is beyond me, it seems that science should have won out over scare tactics. It was leaded gasoline that was the problem, Tetra Ethyl lead was where the problem was created.
Last edited:
I read through the original NASA analysis paper a few years back. They had a detailed software state diagram, where faults caused specific states that the system hung at. Orange states were the bad ones, yellow were safe ones, and half the end states were orange...
I'll try to find that, I used it to convince the higher ups here that going lead free was not a good thing. Luckily, I convinced them..
jn
ps. The trailer on the EDN website, the links are broken...
""Several accelerator pedal position sensors had tin whiskers that could cause short circuits, according to a NASA paper. The paper, delivered at the International Tin Whisker Symposium, reported on tin whisker growth in Toyota accelerator pedal position sensors that, depending on pedal rate of movement, could lead to unintended acceleration.""
There was an International Tin Whisker Symposium?? Who'da thunk..
edit: here's the original paper, page 9 has that flow diagram with the orange "not so great to be here" circles..
http://nepp.nasa.gov/whisker/reference/tech_papers/2011-NASA-GSFC-whisker-failure-app-sensor.pdf
Last edited:
I can see if that happened ETC would stay open, but what about brake pedal override, did they explain why the brake override function never worked. Easy to verify with ETC, just try the old brake and gas technique, if it does not return to idle in 3-5 second(with ET wide open) then i would walk away from that one ..
I can see if that happened ETC would stay open, but what about brake pedal override, did they explain why the brake override function never worked. Easy to verify with ETC, just try the old brake and gas technique, if it does not return to idle in 3-5 second(with ET wide open) then i would walk away from that one ..
I can't answer those questions. It would seem that you know far more about this than I, obvious from the fact that I've been sitting here reading your last two posts, staring and drooling..
jn
What? You mean it wasn't a bunch of limp-wristed, pasty-faced, raw vegan environmentalists?
se
You forgot lily livered..
jn
Mass hysteria promoted through flawed science used to influence legislatures is more likely the culprit here. So much junk science that sounds reasonable on the face of it but doesn't hold up to scrutiny when actually examined is what we so often have to deal with. Seems like every week we here eggs are bad and then they are good, don't eat this and then it is good for you, so much nonsense all the time.
a.wayne,
I have never noticed that there was a brake override in the ladder logic of the cpu that uses the brakes as the master logic. I'll see if that is mentioned in my manual but don't remember seeing that anywhere in the factory manual before. I know it messes with some of the sensor tests if you touch the brake on coast down and such but never tried to step on both pedals at once, I don't use both feet except when I have a clutch pedal. I assume that most times I see an accident caused by someone driving through the front of a business it is someone stepping on the throttle and thinking they are on the brake, especially those who use two feet, one on the brake and one on the gas.
a.wayne,
I have never noticed that there was a brake override in the ladder logic of the cpu that uses the brakes as the master logic. I'll see if that is mentioned in my manual but don't remember seeing that anywhere in the factory manual before. I know it messes with some of the sensor tests if you touch the brake on coast down and such but never tried to step on both pedals at once, I don't use both feet except when I have a clutch pedal. I assume that most times I see an accident caused by someone driving through the front of a business it is someone stepping on the throttle and thinking they are on the brake, especially those who use two feet, one on the brake and one on the gas.
- Status
- Not open for further replies.