Hello all,
We are having a hard time finding a suitable microcontroller for our new automotive project. The product will have to operate in a very harsh enviroment including temperatures lower than -40 deg. C.
Most microcontroller has -40 deg. C. as the lowest limit. Anyone here knows of microcontrollers that maybe goes to -50 deg. C. ?
All architectures are welcome!
Best Regards
Morten M. Jørgensen
a microcontroller with a heater?.
.... space electronics use microheaters to keep the electronics within a useable working band. Normally by careful layout and appropriate insulation/heatsinking you can redistribute the system hotspots and get the heating for free. All part of the design process I am afraid.
atmega32 -55c to +125c
just plucked that one out of the box, didn't need to search.
see:
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Put the microcontoller between the driver's thighs. If it drops below
-40 there, nobody's going anywhere.
All chip that respect military temperature range goes from -55°C to
+125°C.I think you should be able to find some...
-- Guillaume Chevillot
Since the application is a small footprint temperature sensor I don't think this will do. I think it will be hard to control the influence of the heater !?!?
-- Morten "Icky Thwacket" skrev i en meddelelse news:4695db7c$0$1613$ snipped-for-privacy@ptn-nntp-reader02.plus.net...
The operating range states:
-40 to 85 deg. C.
The absolute maximum ratings states: 55 deg. C.
I looking for at controller which includes below -40 within its operational/working range.
-- Morten
"D>
Glad I was not drinking anything when I read that one.... :))
-jg
In news:4695d93b$0$193$ snipped-for-privacy@dread11.news.tele.dk timestamped Thu,
12 Jul 2007 09:33:20 +0200, "Morten M Jørgensen" posted: |---------------------------------------------------------------------------| |"Hello all, | | | |We are having a hard time finding a suitable microcontroller for our new | |automotive project. The product will have to operate in a very harsh | |enviroment including temperatures lower than -40 deg. C. | | | |Most microcontroller has -40 deg. C. as the lowest limit. Anyone here knows| |of microcontrollers that maybe goes to -50 deg. C. ? | | | |All architectures are welcome! | | | |Best Regards | | | |Morten M. Jørgensen" | |---------------------------------------------------------------------------|Hello,
A suitable but excessive device would be one designed for use in space, e.g. a field programmable gate array for space from Aeroflex (
If you speak to Aeroflex and Silicon Laude, they may be able to suggest some division other than its astronautical division which might make devices which are suitably cheap for you but still adequate for a low temperature.
Regards, Colin Paul Gloster
In addition to the other comments I'd recommend not running your clock close to the highest rated speed, and I'd also have you check on the ratings of supporting components such as capactitors and XTAL oscilators.
A/D conversion is likely to be spotty near the temperature extremes also (check the spec sheets carefully - I know that Silabs is one company that specs A/D for the whole temp range but I don't know about the others). I'd design the whole system with at least a 20% margin to hedge my bet.
Eric
Do you really need the microcontroller to be part of the temperature sensor assembly?
Dealing as I do in cryogenic temperature measurements we go to a great deal of effort to ensure we thermally ground the wiring to our sensors (4 wire plan always). This way we can be sure that the temperature sensed is that of the point we are monitoring and not the heating effect of the current flowing in the wiring (even a few uA is enough heat to give several degrees Kelvin error). We also take care with the source energisation to minimise the battery like effects at wiring junctions (plugs and sockets etc).
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A little more seriously, can anyone give a simple explanation as to why low temperatures are a problem for solid-state electronics? Do the eletrons freeze?
When I talked to a Microchip Rep about using their chips for operating down to -76 deg C they said that one of the problems is differential expantion/contraction between the die and the package. At that temperature the die often will crack.
Don
Exactly. I am trying to explain it without going into details; it is actually lot more complicated.
The behavior of a semiconductor material depends on how many charge carriers can jump across the energy gap from valent to conduction zone. The average energy of the charge carriers depends on the temperature. So, at low temperatures the semiconductor material behaves like a dielectric, and at high temperatures it behaves like a metal. A semiconductor acts as a semiconductor only within a range of temperatures.
Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
That is more a storage temperature issue.
For bipolar silicon devices. the junction forward voltage drop has a temperature coefficient about -2 mV/C so with a junction temperature from -55 C to +200 C, for instance the transistor Vbe can vary about
500 mV, so extra care is required in designing the biasing arrangement. This can be problematic in low voltage battery operated systems, especially as the battery voltage also drops with temperature.Also the bipolar current gain drops significantly with temperature and in oscillators the active device gain must be able to compensate for the resonator losses i.e. the total loop gain must be at least 1. At low temperatures the total loop gain may be below 1, in which case oscillation is not possible. It can take a few seconds or a few minutes, before the bias current warms the transistor sufficiently, to increase the current gain and thus making oscillation possible.
There are a large number of ways things can go wrong and if a module manufacturer has a heat/cold test unit that goes only down to -40 C, the published temperature range is limited to -40 C, even if the unit would in practice function reliably at lower temperatures.
Paul
ws
I've worked on military products where we have to be fully operation at -55 Deg C, previously you could buy these off the shelf, but most manufacterers don't offer them anymore. What we do now is buy -40 Deg parts and screen them (test them at -55 Deg C), there are companies that can do this for you.
What sort of yield do you get doing this, and how does it vary across parts ?
-jg
The Freescale MPC555, MPC566 and MPC5554 are all available in -55 to
125 degrees. I believe they are the standard devices tested to extended temperature.They're not cheap though. They are about $120 each in quantity, compared with approx $50 for the -40 to 125 devices.
Andy Sinclair
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