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DRV8323R: VGLS voltage swing

Konrad Holzmann
Prodigy 120 points
Part Number: DRV8323R
Other Parts Discussed in Thread: DRV8323

Hello,

My initial issue was, that my motor makes some noise at a static duty cylce and 40kHz.

I'm using a DRV8323RS three phase gate driver and wondering about the gate voltage at the low side mosfets. Vm is about 24V and gate voltage is between 10V and 16V, see scope capture. The variation in gate voltage causes some variation in the switch off time, further it causes some small change in the resulting duty cycle, what further causes some current changes and I think, that is the noise what I can hear.

Is this voltage swing normal? What could be wrong?

Regards, Konrad

  • 0
    TI__Guru** 114905 points
    Hi Konrad,

    Do you see this on all three low side gate voltages?
    Do you see this on multiple boards?
    The low side gate voltage should be less than 12V.
  • 0 in reply to Rick Duncan
    Prodigy 120 points
    Hi Rick,

    yes I can see similar signals on all low side gates. At the momement I only have one prototype board with two DRV8323 parts and both parts show the same behaviour. The low side gate voltage is definitly over 12V and I am afraid of damaging the MOSFET if the gate voltage is not controlled well.

    In the meantime I experimented with the gate driving current. When i set IDRIVEP_LS to 1100b the gate voltage behaves like expected. The captured picture was with IDRIVEP_LS = 1111b.

    Regards
    Konrad
  • 0 in reply to Konrad Holzmann
    Prodigy 120 points

    Hi Rick,

    one further issue.

    Now I experimented with some different duty cycle. There I get the attached captures. One cycle the gate voltages are correct (below 12V) in the next cycle they are too high. The interesting thing is the rising edge after the abnormal cycle. The gate voltage is rising very slow, both gates are rising in the same way. It seems that the gate voltage regulator was disabled because of too high voltage?

    Regards

    Konrad

  • 0
    Prodigy 120 points
    Hello!

    Any assistance to my problem regarding the high voltage on low side gates?