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Chip temperature ratings?

Discussion in 'Electronic Basics' started by Glenn Ashmore, Feb 25, 2004.

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  1. What happens when a chip is colder than its rating? Say I have a choice
    of 2 versions of the same chip. On rated for 0-70C for $.76 and the
    other rated -4-85C for $4.96. The non-critical circuit will be in a box
    outside where once in a VERY rare while it may be called on to operate
    at -5C. Is it not going to work or just maybe not going to work?

    Glenn Ashmore

    I'm building a 45' cutter in strip/composite. Watch my progress (or lack
    there of) at:
    Shameless Commercial Division:
  2. Gareth

    Gareth Guest

    I can't imagine any chip suddenly stopping completely when the
    temperature gets to 0C, but it may not meet its spec in some way, for
    example a voltage regulator may have a higher voltage drop out than
    expected, or an oscillator will be a bit off frequency. What exactly is it?

    The other thing to consider is that though the outside temperature is
    -5C the temperature in the box will probably be a bit higher if the
    electronics is running.

    It will probably work.


  3. The chip that has the largest price difference (about $4 difference at
    Digikey and back ordered)is an RS422/485 transmitter/receiver that links
    a cockpit lighting control to a digital switch in the cabin. All the
    other -40C chips are fairly cheap and the PIC goes to -55C.

    I have to say that I have added a manual override and it is highly
    unlikely that it would ever see -5C as I am a thin blooded South Georgia
    sailor who has no intention of sailing north of the Mason Dixon line
    between September and May. :)
    Glenn Ashmore

    I'm building a 45' cutter in strip/composite. Watch my progress (or lack
    there of) at:
    Shameless Commercial Division:
  4. CFoley1064

    CFoley1064 Guest

    Subject: Chip temperature ratings?
    One of the things you get with the extended temperature range is more
    resistance to humidity and moisture getting into the chip (look at the side of
    commercial chips -- you'll sometimes see the metal from the leadframe sticking
    out the east or west sides of the chip).

    Most of your stuff has to do with marine applications anyway, so you probably
    already use a conformal coating over your boards to prevent corrosion. If
    you're planning on occasional extremes of cold, you might want to consider a
    conformal coating to reduce the chance of humidity or condensation (which you
    will get with excursions below 0C, possibility of salt in the air making things
    orders of magnitude worse) getting into the chip. Apart from that, it's not an
    engineered solution, but it should work fairly reliably.

    Good luck, and fair weather, sir.
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