TPS3839: Reset signal problem while IC is being exposed to strong light

N Nakamura,

I will need to look into this more. I don't believe light can affect the performance but I will do some testing and let you know when I have more information. I would like to note that the TPS3839 has an active-low /RESET which means the /RESET will be high as long as VDD is above the threshold voltage. If VDD drops below the voltage threshold, the /RESET drops low and remains low until a delay after VDD comes back up. Is this situation what you are observing or something different?

Respectfully

-Michael

Dear Michael

Thank you for your comment.

We observe something different, the following issue.

The IC is "TPS3839L30".
If the IC is not exposed to strong light,
the /RESET will be high after VDD is above the threshold voltage.
VDD keeps stable (~3.3V) above the thresholod volatage (=2.63V) and the RESET stays high.

But under the condition that the IC is being exposed to strong light,
after VDD is going up to above the threshold voltage, the /RESET will be not high.

Once the /RESET become high, the /RESET stays high even if the IC get exposed to the strong light.

We go on checking this issue.

I appreciate your consideration.

Best regards,

N. Nakamura

N. Nakamura,

In order to accurately investigate the issue, I need to know the package for the device you are using. Please provide the Orderable Device Part Name found in the Package Option Addendum at the end of the datasheet.

Respectfully,

Michael

Dear Michael

 

The Orderable Device Part Name is "TPS3839L30DQNT".

 

Thank you for your kind investigation.

 

Best regards,

 

N. Nakamura

We've confirmed that

- this issue occurs on the Evaluation module.

- this issue does not occur on the IC covered by light shielding material

 

I know there may be no specification under strong light exposure,

but It would be appreciated if there is information of similar case, test result, the consideration of the possibility and so on.

If so, let me know by direct e-mail of my profile.

 

Best regards,

N Nakamura,

From my understanding, the specific part package is X2SON which is completely sealed from light meaning light exposure should not be able to penetrate into device. However, we believe their issues could be caused by either:
1. The laser is heating up the part enough to bring the device outside of its recommended temperature range. Please have measure the temperature with the laser on the device.
2. Or we think that it is possible the laser is strong enough to penetrate through the mold compound of the device. Please try with a less intense light such as a flashlight which doesn’t have as small wavelength and is not as intense and see if the issue still remains.
3. Also, have you seen this issue consistent each time you use the laser the device fails? Is this happening on multiple devices?
4. We are trying to replicate the issue but have not be able to yet. I will have our bench results by end of today or tomorrow at the latest.


-Respectfully
Michael

Dear Michael

Thank you for your consideration.

We observed
- no heating up of IC by laser exposure.
- weaker laser doesn't cause this issue.

We asked TI Japan face to face about this issue yesterday, and got the same answer from them today as your comment.
To unify these exchanges, let us have the exchange through TI Japan mainly.

It may be appreciated if your results were just to be shared here.

Best Regards,