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DRV8320: DRV8320H - problems with latched nFault

Part Number: DRV8320

I use the DRV8320H to drive a B6 bridge for steering a sensorless BLDC motor. During operation esp. at higher output currents the driver stops sometimes operation due to latched nFault. This occurs sometimes very short time after start PWM (50...100ms), at high output current of the B6 bridge.
The VDS detection is disabled (VDS pin tied to DVDD). So the only reason for a latched nFault is GDF fault. But based on my measurements there should be no reason for a GDF.

My question is: what could I measure to find out the root cause or what should I change on the configuration? Maybe the disabling of VDS detection is unstable?

For further details of my application please refer to the thread "BOOSTXL-DRV8320H: Charge Pump --> too high High Side Gate Source voltage".
Below I add some osci screenshots for better understanding:
At all screenshots: channel 1 = nFault, channel 2 = motor phase current
1. screenshot: nFault active after some ms of operation, no SW reset implemented no (reset of nFault by disable and enable the driver)

2. screenshot: nFault active after some ms of operation, SW reset implemented (reset of nFault by disable and enable the driver)


  • Martin,

    As in your previous post, you should check the voltage of gate to source for all six gates. If any of the gates are not reaching their saturation point before TDRIVE ends then you will see a GDF. Also if any gate is seeing more than ~2-3V during the time that it is supposed to be OFF then you will see a GDF.

    Regards,

    -Adam