• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 63 subscribers
  • Views 158 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM1117: Material Difference for Operating Temperature Discrepancy

Andrew Oglesby
Prodigy 20 points
Part Number: LM1117

Hi,

I'm looking at the datasheet for LM1117 voltage regulators. I'm wondering what the difference is between the standard LM1117 and LM1117I that drives the operational temperature difference. Is there a material or construction difference between the two?

What is the risk of using the standard LM1117 on startup at -46C and operating at -32C? I understand that the part may fail, but how would be most important. Whether the device will be damaged or just not maintain specified tolerances.

Thanks

  • 0
    TI__Mastermind 38485 points

    Hi Andrew,

    It is difficult to say why the LM1117 is only recommended to operate down to 0C because this is an older part. It may be that the behavior starts to deviate from the intended specs, and they chose to only recommend down to 0C to avoid weird behavior. 

    I believe that the part won't be damaged if the junction temperature falls slightly below the minimum recommended temperature. As you said, it is more so that the part is not guaranteed to work within specs if it is operated outside of the recommended range.

    Best regards,

    Nick

  • 0 in reply to Nick Butts
    Prodigy 20 points

    Thanks for the info. Do you have a rough order of magnitude on how much the regulator might deviate at a startup of -46C? Would it be something like 1%, 10% etc in a specific direction? Also, is it load dependent?

    We would be grateful for any advice you could offer.

  • 0 in reply to Andrew Oglesby
    TI__Mastermind 38485 points

    Hi Andrew,

    Figure 6 has data down to -50C, so you can see here that the percentage deviation is less than 1% in the negative direction. 

    The output accuracy is always load dependent to some extent. Figure 3 shows that at -50C and max load there is an additional ~.15% in the negative direction deviation:

    Just FYI, if the junction temperature is too low, it is possible that the internal bandgap voltage reference may not start up and so the whole part will not start up. -46C is not too far out of the recommended range, so it probably won't be an issue here, but that is something to keep in mind when dealing with low temperatures. 

    Best regards,

    Nick