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TLV702: TLV70233 Intermittent Output Dropout Issue

Ching-An Chen
Prodigy 20 points
Part Number: TLV702

Hi team,

We have encountered the following issue: 
TLV70233 Intermittent Output(3.3V) Dropout.
the client observes no output at 3.3V. However, upon returning to the factory, we were unable to reproduce the problem.

here is some information we observed.
1.  the maximum output current is 100mA.
2.  the input should be stable .
3.  Ambient temperature is about 35°C.
4.  the output capacitance is nearly 25uF.
5.  These are newly produced circuit boards and coated entirely with conformal coating.

What experiment I have tried but can't reproduce the issue:
1. thermal test: -40°C~100°C
2. Dynamic load: 100mA~400mA
3. pollution experiment

Are there any relevant cases or possible methods to reproduce the issue?

  • 0
    TI__Mastermind 49485 points

    Hi Ching-an,

    I don't see anything with the schematic that would cause an issue, and I also looked and was unable to find any documentation of past issues that sound like this issue for this device. 

    When you tested at the factory, did you test with the devices still on the board or did you remove them to test? When the device was not regulating to 3.3V, was it verified that the supervisor was outputting a high signal for the EN pin? Was the device hot to the tough when there was no 3.3V?

    Regards,

    Nick

  • 0 in reply to Nick Butts
    Prodigy 20 points

    Hi Nick,

    thx for your reply.

    Here are the answers  to your question and other information:
    1. the device is always on board.
    2. we have another circuit using thw same 5V and supervisor to having another 3.3V, but this 3.3V is stable. So we infer that the enable pin signal is good.
    3. we could not know is it hot or not when the 3.3V disappear (it only happens at end customer).

    4. the event duration is about 200ms ~1.5s.
    5. it happened about 5 times per day.

    We are completely puzzled by this, and at the same time, we are unable to speculate on the reasons.
    Therefore, we would like to inquire whether TI has any relevant incidents in database regarding this issue with the LDO that we can refer to.

  • 0 in reply to Ching-An Chen
    TI__Mastermind 49485 points

    Hi Ching-An,

    It looks like there are actually 2 separate supervisors, which are the same part number. Is that correct? Just want to confirm. It seems likely that if one was working, the other would be as well.

    Without waveforms or any other information about the failure, it is difficult for us to speculate as well, especially since the schematic implementation looks good. There could be some voltage transient on the power line that causes some undesired behavior, and without seeing those kinds of waveforms during the event there is not a lot we can do to troubleshoot this.

    Regards,

    Nick

  • 0 in reply to Nick Butts
    Prodigy 20 points

    Hi Nick,

    thanks for your review.

    yep, we have 2  separate supervisors, one for dsp power(buck converter) another one for sensor(LDO). and we confirm DSP was working, so the supervisor
    should worked well.

    here is the waveform that DSP recoreded at the event: 
    Sample rate = 200 ms
    3.3V drop time = 400ms

    I'm waiting for another client who encountered this issue; perhaps we can have someone on the spot who can give us more information.

    thanks again for your help.

  • 0 in reply to Ching-An Chen
    TI__Mastermind 49485 points

    Hi Ching-An,

    Got it. 

    Unfortunately a period of 200ms is far too long to see any details of what was happening during this event, and more importantly we would need to see what was happening at the input as well to determine what could have happened to cause the event. So, I'll have to wait and hope that the other customer can provide more data because at this point there isn't enough for me to work with.

    Regards,

    Nick