Why do we consider temperatures -40 and 125 deg as the extreme ones?

[iVenky]

In simulations we always check the circuit for PVT variations. Why do we consider -40 °C and 125 °C as the extreme temperatures. Any specific reason behind it?

Thanks

 

[kripacharya]

I think these are based on extreme human conditions that we want to design for. Other than that its fairly arbitrary.

 

[dick_freebird]

You may consider these the extremes. I don't. I've done ICs
that worked as low as 40K and as high as 300C.

-40 is common for "industrial" low end, -55C is called out
by many military systems; 85C and 125C are common at
the high end.

Your customer makes the call, either explicitly or by
reference to what -their- customer has demanded.

 

[andre_luis]

I believe those values were conventionally adopted due to be easily reached at extreme environmental circumstances, such as at equipments working at flying cruising altitude at polar latitudes, or inside casing directly hit by sunlight radiation.

In fact [-40/125] makes more sense to choose some 5x or 10x multiply value than other ones as for instance [-41/124], [-39/123], etc...


+++

 

[xingkongwu]

good explaination

You may consider these the extremes. I don't. I've done ICs
that worked as low as 40K and as high as 300C.

-40 is common for "industrial" low end, -55C is called out
by many military systems; 85C and 125C are common at
the high end.

Your customer makes the call, either explicitly or by
reference to what -their- customer has demanded.

 

[diarmuid]

as per the above post it is largely application dependant.

General IC design sets the lower limit at -40degC.

I have worked with upper limits of 100degC (mobile), 125degC and 150degC (automotive).

Correct calculation of upper limit is as follows:

Determine max ambient temp of the IC.
Determine max power consumption of the IC.
Using the thermal resistance of the package, calculate the junction temperature at
this max ambient temp / power consumption.
The result is your max junction temperature i.e. the high temp you should run your sims at.

Ensure your max temp has been calculated in this way. I have worked on ICs where too low
a junction temperature was calculated as the above was not done. The result ... the IC leaked
like crazy at the max ambient temperature in the lab!!! Re-tape out time!