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LM317L-N: Light Sensitivity

Part Number: LM317L-N
Other Parts Discussed in Thread: LM317

Hello Team,

Earlier one of the engineers I am working with asked a question regarding light sensitivity concerns on the LM317L-N. 

Specifically, they noted that we used to have a section in the datasheet that highlighted the concern that exposing the package to bright sunlight may cause a drop in Vref. Attached are screenshots of the old datasheets. Now, the datasheet on TI.com does not have this comment, so I wanted to understand if this concern is still valid?

  

Since it was removed from the datasheet, does that mean that the engineer does not need to take this into consideration and we implemented something new in our process to address this?

Any feedback or help on this would be appreciated. 

Best Regards,

Javier Palomo

  • Hi Javier,

    This section is still in the datasheet.  On the current revision it is section 7.4.3 DSBGA Light Sensitivity:

    Very Respectfully,

    Ryan

  • Ryan,

    Good call, I must have been looking at the LM317 datasheet and not the "L-N" version. Thank you for correcting me on this!

    That being said, can you explain why this occurs, or is there resource where we can get more information on this? The engineer I am working with is going to run a light exposure test, so it will be nice to have a better understanding on this condition.

    Best Regards,

    Javier Palomo

  • Hi Javier,

    The energy from the light is able to penetrate into the die of the linear regulator. This energy will change the internal node voltages/currents. While this will not damage the regulator, it will alter the reference voltage and therefore the output of the LM317L-N. As such if using LM317L-N in a DSBGA package, we would recommend shielding it from light sources.

    Very Respectfully,
    Ryan
  • Hi Ryan,

    Okay, thank you for that explanation and for your help!

    Best Regards,
    Javier Palomo