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LM5176: LM5176 Output Failure – Buck-Boost Mode Issue (VIN < 20V)

Jian Wei Lai
Prodigy 120 points
Other Parts Discussed in Thread: LM5176

Hi Support Team,

We are working on a project using the LM5176 in Buck-Boost configuration, with the following operating conditions:
VIN = 9–48V, VOUT = 20V, IOUT_MAX = 12A.

During development, not all functions were fully utilized, so we used a 12V / 5A power supply for testing.
The system had been working normally for several weeks, but starting yesterday, it suddenly failed to power up.

We’ve confirmed that the LM5176 output is now abnormal:

  • When VIN < 20V, the output is only around 3V.

  • When VIN ≥ 20V, the output is correctly regulated to 20V, as if it's working in Buck mode only.

  • We also noticed signs of possible damage on the PAD of the high-side MOSFET (Q64), which appears slightly burned.

Please find the schematic and layout attached.
We would greatly appreciate your help in reviewing the design and providing any recommendations or possible causes for this failure.

Thank you for your support.

Best regards,
Woody.

ENVP_JAO_IV_A02_LM5176_DC INPUT_20250110.pdfENVP_JAO_IV-A02_cn7.zip

  • 0
    TI__Guru 58641 points

    HI Woody,

    i could not see an issue in the schematic and layout on an initial review.

    As  next step I recommend to check the power stage esp.:

    - SWx for under and overshoots violating the abs max ratings.

    - checking the timing of the gate signals for dead time violations.

    Best regards,

     Stefan