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OPT8241: A problem of the ILLUM_EN signal

Chris_Wang
Prodigy 180 points
Part Number: OPT8241

Hi guys:

I found a problem of the ILLUM_EN signal. In normal situation, the ILLUM_EN signal is low and then turn to active mode. But in abnormal situation, ILLUM_EN will turn high for about 1400ms then turn low and then turn to active mode.

Hope you can help me !

Regards,

Chris

  • 0
    TI__Expert 3495 points
    Chris,

    Could you please provide the steps to reproduce this condition? If not easily reproducible, how often does it happen? it would be good to also capture ILLUM_P and ILLUM_N at the same time.

    -Larry
  • 0 in reply to Larry Li
    Prodigy 180 points
    Hi Larry,

    It's hard to say how to repeat this situation.But it can be found when turn off the power then turn on the power quickly.Most of our machines do not happen this, the probability is about 5/100. I will capture the ILLUM signal tomorrow as soon as possible. Thanks!

    Regards,
    Chris
  • 0 in reply to Chris_Wang
    TI__Expert 3495 points
    Hi Chris,

    I assumed you measured ILLUM_EN right at OPT8241's pin, not through any driver/logic buffer, correct?

    -Larry
  • 0 in reply to Larry Li
    Prodigy 180 points

    Hi Larry,

    You are right, the ILLUM_EN signal has been measured right at OPT8241' pin. As you can see from the two pictures below. When there happened the problem, there was a constant high level for about 400ms in the ILLUM_EN signal. The ILLUM_N has been choosen to drive the LEDs, so when there is  high level in ILLUM_EN, the ILLUM_N is also high, it will cause the lighting circuit to short circuit.

    Some of our machines will happen the abnormal situation when turn off the power and turn on the power quickly.

    Regards,

    Chris

    Normal

    Abnormal

  • 0 in reply to Larry Li
    Prodigy 180 points
    Hi Larry,

    One more thing, there is another regular phenomenon, if the turn off time is long than about 1 minute, the abnormal situation will not happen.

    regards,
    Chris
  • 0 in reply to Chris_Wang
    TI__Expert 3495 points
    Chris,

    is this issue resolved? I think the startup sequence does matter.

    -Larry
  • 0 in reply to Larry Li
    Prodigy 180 points
    Larry,
    The issue is still in there, we have to change the power circuit.
    Regards,
    Chris
  • 0 in reply to Chris_Wang
    TI__Expert 3800 points
    Chris,

    I'm reiterating just to clarify the situation:

    The camera boots properly when you normally power it up. However, when you stop and start the camera right after, ILLUM_EN behaves erratically.

    This seems like to be an issue with the way the power rails go down after the camera turns off. Perhaps some of the power rails are not going down to 0 by the time you restart the camera.
    Do you think you can monitor the power supplies and find out which supply is not going to 0 after turn off?

    Regards,
    Subhash