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LM317A: Temperature Protection of LM317A

Oz Kocoglu
Intellectual 270 points
Part Number: LM317A
Other Parts Discussed in Thread: LM317

Hi,

I have the following question:

At normal operation, the Operating Temperature Range of  LM317A is at  -40 to 125°C.In case of an abnormal operation (e.g. shortcut at the output), the device could reach higher temperatures.

If I understood correctly the built in thermal protection will react at around 150°C and reduce the current. How long can the device stay in this condition of 150°C (thermal shutdown) without getting damaged ? 

Thanks and best regards

  • 0
    TI__Prodigy 515 points
    If the output is shorted to ground, the LDO will cycle on and off and lead to increase of temperature. Once the temperature reach the threshold(150degC), the thermal shutdown occurs. The drive to the transistor is cutoff and the internal power dissipation is reduced( both voltage and current can be reduced) to protect the device from being damaging.
    Operating under high temperature stresses the device and degrades reliability. It isn’t recommended to use over 125degC for a long period of time.
  • 0
    Guru 140200 points
    Hi Oz,

    some variants of LM317 have to pass a burn-in in thermal limit. They must withstand the thermal limit for about 5 minutes if I remember correctly.

    Well, the LM317 should be able to withstand this torture for many hours but it will definitely suffer the more the longer the barbecueing is lasting and the more often it is happening. As Min already mentioned this will definitely decrease reliability and lifetime of LM317.

    Kai