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Original question:

TPS92692: Not starting properly in boost configuration

TPS92692-Q1: IC failure (VIN present on VCC and VREF)

Thijs Kessels
Prodigy 10 points
Part Number: TPS92692-Q1

Tool/software:

hi TI,

I received a message from our customer that a lamp had failed that uses the TPS92692-Q1 controller (boost mode).
After disassembly, it turned out that the voltage applied to VIN was present on both VCC and VREF. I could not find a short-circuit on the PCB (with and without the IC on the PCB).

VCC is only connected to a decoupling capacitor
VREF has a couple of 7400-series logic, an opamp and a comparator connected, (and associated decoupling capacitors).

Is this a known failure mode? Any guidance would be helpful.

  • 0
    TI__Expert 5750 points

    Hi Thijs,

    Is this happening with multiple boards or just a single board?
    Can you please post the input/ output requirements and switching frequency, the schematic, and the following wave forms?

    Inductor current
    Switch node voltage
    fault pin if it is present on the IC
    Input voltage
    Output voltage
    any other wave forms that provide me information on the issue that is occurring

    I look forward to resolving your issue in a timely fashion.

    Best,
    Daniel

  • 0 in reply to Daniel Louis
    Prodigy 10 points

    hi Daniel,

    This has happened on a single prototype board.

    Input is 12V (9-16V), output is 200mA at 42V, 432 kHz switching frequency.

    U2 is supplied from VREF

    There is some more circuit below, but that has been disabled.

    Because we needed a containment action for the customer I was not able to measure the faulty board beyond checking for shorts and damage to the PCB before moving on towards getting the customer going again. I also needed to re-use the faulty PCB in the lamp for that 'fix', so I sadly don't have access to the PCB to capture waveforms.

    The lamp has been in the test mule vehicle for driving tests, so it could be from customer testing, but I did not notice any damage around the TVS (D6).

    kind regards,

    Thijs

  • 0 in reply to Thijs Kessels
    TI__Expert 5750 points

    Hi Thijs,

    Unfortunately this is not a known mode of failure and the IC is likely damaged. Please contact the quality team and have them evaluate the part. Meanwhile, you can try replacing the IC with a known good one.

    Sorry, there is not much more I can do without wave forms

    Best,
    Daniel

  • 0 in reply to Daniel Louis
    Prodigy 10 points

    hi Daniel,

    apologies for the delayed response. I'll replace the IC next opportunity I get

    Understandable that not much can be done without waveforms. Thanks for the support anyways

  • 0 in reply to Thijs Kessels
    TI__Expert 5750 points

    Hi Thijs,

    I wanted to follow up and make sure this issue has been resolved. Please let me know if there is anything I can do to help.

    Best,
    Daniel