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UCC27714: HO output permanently high

Faraz Ahmad
Prodigy 50 points
Part Number: UCC27714

Tool/software:

Hi Community,

Hope you are doing good. Currently I am using UCC27714 IC as a gate driver for LLC in half bridge configuration. I am getting a "permanently high on HO output" while LO is working fine. Both the HI and LI pin are fine.

Changed the IC, mosfets multiple times. Still the issue persists. Does anyone have any idea what could be wrong?

Thank You

  • 0
    TI__Genius 14145 points

    Hey,

    Thank you for reaching out to TI with your questions regarding the UCC27714.

    I have a few questions to help understand the situation that you are seeing.

    1) Can you share the schematic as well as waveform captures of this?

    2) How many boards do you have and how many does this show up on? How many gate drivers have you seen this issue with and are the MOSFETs failing first?

    3) If HO is high and you drive LO high, you will see a shoot through condition and damage the MOSFETs and most likely the gate driver also.

    4) Are there any other components on the board that are being damaged or could be shorting causing this issue?

    Let me know if you have any questions.

    Thank you,

    William Moore

  • 0 in reply to William Moore
    Prodigy 50 points

    1. Schematic of gate drive circuit and gate drive waveforms are shared. The Green trace is of high side drive, Low side drive is perfectly fine.

    2. This is the first time I am seeing this kind of issue, Other boards are perfectly fine.

    3. MOSFETS won't fail as we are only checking gate drive, we are giving 0 DC voltage, juts powered up the drive.

    4. Your 4th point may be the real cause, But I need to know what is going wrong with the IC.

  • 0 in reply to Faraz Ahmad
    TI__Genius 14145 points

    Hey Faraz,

    1. Is the measurement on Channel 4 done with a differential probe from HO-HS? If not, that would be helpful to see what the Vgs of the FET is.

    2. Also, can you take a measurement of HS-VSS to see what the switch node is doing in this state?

    3. What is the output stage and the status of HS during this instance? If HS is floating with no output, the high-side will not pull down to ground.

    4. Also, what is the 20uH inductor on LO and HO for? That should not be there.

    5. So there are other boards that are identical to this one and not having issues?

    Let me know if you have any questions.

    Thank you,

    William Moore

  • 0 in reply to William Moore
    TI__Genius 14145 points

    Hey Faraz,

    Were you able to resolve this issue? If so, can you please share your findings?

    If not, can you please respond to my questions above and update me on the status of what you are seeing?

    Thank you,

    William Moore

  • 0 in reply to William Moore
    TI__Genius 14145 points

    Hey Faraz,

    I am going to close this thread at this time. If you have further questions or updates regarding this issue, please feel free to reopen and update this thread.

    Thank you,

    William Moore