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The LM317 chip has an operating temperature range of 0 to 125 degrees Celsius. What happens if I use it at low (negative) temperatures? Will it work? What parameters will be affected by the temperature?

I know about the existence of the LM317M and LM317A, but I'm wondering what the temperature affects.

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  • \$\begingroup\$ Have you read the data sheet to see what it says? \$\endgroup\$
    – Andy aka
    Commented Dec 6, 2022 at 10:10
  • \$\begingroup\$ @"Andy aka" Datasheet from TI LM317 In terms of recommended parameters (not absolute maximum), there is an item: TJ Operating virtual junction temperature 0 .. 125 °C Other data rather relate to the upper temperature limit. \$\endgroup\$
    – Stress
    Commented Dec 6, 2022 at 12:03

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The thing with specifications is that when used within the specs the part is guaranteed to behave as specified, and when used outside the specs, the part is not guaranteed to work at all.

Surely there is a margin for manufacturing tolerance and defects that allow the parts to be binned for narrower or larger temperature range.

And each manufacturer may manufacture the parts in their own specific way so there is no general answer how your specific part will behave when you bring it to lower temperatures than specified.

It depends on the manufacturer, manufacturing tolerances and which unique properties the parts you bought happens to have.

You might be able to guess how it will behave, if you open up the manufacturer datasheet for the part and seek any parameters or curves that are listed at different temperatures.

To guess what might happen, i.e. what can be out of specified tolerances :

  1. Output voltage may be higher
  2. Output voltage may be lower
  3. Output load regulation may be worse
  4. Output thermal regulation may be worse
  5. Adjust pin current may be vary more
  6. Output max current may be more or less
  7. Output short circuit current may be more or less
  8. Ripple rejection can be worse
  9. Dropout voltage may be more or less

Bear in mind that temperature does not only affect the regulator, but also nearby parts such as capacitors, so when the temperature changes, so does the capacitance and effective series resistance of capacitors, so as a whole the system may just be a poor and unstable power supply at low temperatures.

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  • \$\begingroup\$ Low temperature may affect most likely the chips body. Plastic may deformate or crack. \$\endgroup\$
    – user263983
    Commented Dec 6, 2022 at 11:13
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    \$\begingroup\$ @user263983 And yet the parts that are rated down to -40 °C come in similar plastic packages. But you are correct, the plastic case material can be different to handle colder temperatures. \$\endgroup\$
    – Justme
    Commented Dec 6, 2022 at 11:15
  • \$\begingroup\$ Note that those parts also have a vbration rating. It could be that they can't fulfill that at low temperatures because some glue or bonding material starts to get brittle. @Justme is 100% right, the Manufacturer does not guarantee that the part behaves like in the datasheet described. It's up to the user to find out ther hard way, which spec it is and if it's relevant for the use case. \$\endgroup\$
    – kruemi
    Commented Dec 6, 2022 at 13:59
  • \$\begingroup\$ The LM317 has some kind of circuitry feature/property. Because a similar situation with temperatures at ST and Onsemi. TI, ST and Onsemi have versions with recommended modes -40 ° C and normal (from 0 ° C). I don't think that everyone has problems with compounds or cases already at 0°C. \$\endgroup\$
    – Stress
    Commented Dec 6, 2022 at 14:23

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