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DRV8329-Q1: DRV8329AQRGFRQ1 – GHC Not Boosting / Bootstrap Capacitor Not Charging

Akshil Goti
Prodigy 10 points
Part Number: DRV8329-Q1


We are facing an issue with the GHC output on the DRV8329AQRGFRQ1.
The bootstrap capacitor for phase C is not charging, so the high-side MOSFET for phase C is not getting the required boosted voltage.

Below are the measured voltage levels (all measured w.r.t. GND):

  • GVDD: 12.2 V

  • PVDD: 12.2 V

  • AVDD: 3.3 V

  • CPL–CPH: 12.2 V

  • nSLEEP / nFAULT: 3.3 V

  • DRVOFF: 0 V

  • GLA, GLB, GLC: 12.2 V

  • GHA, GHB: 19.8 V (expected boosted level)

  • GHC: 12.2 V (no boost — remains at PVDD/GVDD level)

It appears that only phase C bootstrap is not building the charge pump voltage (no increase above PVDD), while phase A and B are working correctly.

Could you please help us understand under what conditions the phase C bootstrap might fail to charge, and what diagnostics we should check next?

  • 0
    TI__Genius 17265 points

    Hi Akshil,

    Can you share your schematic and the MOSFET you are using?

    Can you provide waveforms of each phase for the following:

    GHx w.r.t. SHx

    BSTx w.r.t. SHx

    SHx w.r.t. GND

    GLx w.r.t. GND

    It would be good to have a visual comparison of each phase as the low side turns on, the bootstrap should charge.

    I'm not really sure what could be cause this issue but these waveforms and a schematic will give me a better idea of what is happening.

    Regards,

    Yara