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OPT3002: Is OPT3002 Output increases over time?

user6489437
Prodigy 50 points
Part Number: OPT3002

Hello,

We are using the OPT3002 to detect the illuminance of the green LED.
After firing the green LED for about 200 hours, we measured the output of the OPT3002 and found that the value increased by about 2% from the initial value.
(Supplementally, the OPT3002 has been exposed to green LED light throughout this test.)
Then, when we measured the irradiance of the green LED, the irradiance of the green LED was reduced by about 2% from the initial value.
(See the graph below.)
Normally, the output of the OPT3002 should decrease as the LED irradiance decreases, so we are wondering about this result.
So we want you to tell us the following:

1. Is the output of the OPT3002 likely to change after long-term use even if the amount of light received is constant?
2. Can the spectral response of the OPT3002 change after long-term use?
3. If questions 1 and 2 are no, do you know another reasoning that can explain our test results?
4. Please tell me how to use OPT3002 well to keep the error between OPT3002 output and irradiance small.

Best regards.

  • 0
    TI__Mastermind 25895 points

    Hi,

    1. no

    2. no

    3. This could be related to the test setup if any outside light sources are present. This could also be due to spectral mismatch between irradiance meter and OPT3002 if the spectrum of the green LED is changing at all over time.

    It looks like the graph did not post correctly. If you can provide I can take another look.

    Best,

    Alex

  • 0 in reply to Alex Bhandari-Young
    Prodigy 50 points

    Dear Alex,


    Thank you for your reply.
    I'm sorry I failed to post the graph.
    I posted it again. Is the post successful?

    Graph 1 shows the changes in the output of the OPT3002.
    Graphs 2 and 3 are the results of the spectrum measurement of the green LED.

    At first, we also thought that the spectrum of the green LED had changed, but as a result of the measurement, it was found that the spectrum did not change (see Graph 2).
    So we suspected that the spectral response on the OPT3002 side had changed, not the LED spectrum.

    I am not familiar with the characteristics of semiconductors, so please let me know.
    Is it impossible in principle for the photodiode's responsiveness to change over time in response to heat or the energy of short-wavelength light?


    Regards,

    0143.Graph1(Output change).pdf

    Graph2(spectrum).pdf

  • 0 in reply to user6489437
    TI__Mastermind 25895 points

    Hi,

    Yes this time it worked, thanks. You can see Figure 6. Normalized Response vs Temperature in the datasheet for info on expected drift with temperature, which is wavelength dependent. 

    Could you provide some more details on the test setup. Where the measurement was performed, how the light was directed to the sensor and the reference, etc?

    Best,

    Alex

  • 0 in reply to Alex Bhandari-Young
    Prodigy 50 points

    Hello,

    I checked Figure 6 in the data sheet. In this measurement, the change in room temperature is in a narrow range of 20 to 25 ° C, so I feel that the cause is not limited to temperature-dependent drift.

    We have created a brief overview figure of the test setup. See Figure 1.

    Please let me know if you have any concerns.

    Regards,

    Figure1.pdf

  • 0 in reply to user6489437
    TI__Mastermind 25895 points

    Hi,

    Can you test with opt3002 in the same location as the meter to eliminate any possible system level effects? You could use an opt3002evm or separate 3002 pcb and place side by side with detector to check the drift over time. Do you see this on all units tested? How many units were checked?

    Best,

    Alex

  • 0 in reply to Alex Bhandari-Young
    Prodigy 50 points

    Hello,

    The test was conducted on 4 units, and all 4 units showed the same tendency. (While the irradiance decreased over time, the OPT3002 output increased.)

    As you pointed out, we plan to place the OPT3002 board in the same position as the meter and test it to see how the output changes over time.
    I will post again when new discoveries come out.


    Regards,

  • 0 in reply to user6489437
    TI__Mastermind 25895 points

    Hi,

    Just wanted to follow up here to see if any updates and if you are still needing help with this.

    Best,

    Alex

  • 0 in reply to Alex Bhandari-Young
    Prodigy 50 points

    Hello


    Due to the delay in the experiment, we have not yet obtained the experimental results to show you.
    So I close this case and create another one again after the results are available.
    Thank you for your help.

    Regards,