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DRV8302: Problem when applying load

joanne yoon
Prodigy 20 points
Part Number: DRV8302

Hi,

I am trying to drive a motor (48V, 400W, brushless DC) using the DRV8302.

I drew schematics and made a pcb board, referring to the datasheet and some blogs.

DRV8302_EVM_schematics.pdf


MOSFETs: BSC077N12NS2

M_PWM: 1k-ohm resistor to GND

M_OC: 1k-ohm resistor to GND

GAIN: 1k-ohm resistor to DVDD

OC_ADJ: 0-ohm resistor to DVDD

 

The problem is summarized as follows.

1. The high side gate signal is abnormal.


 

2. When a load is applied, noise is severe on the power line(pvdd, gvdd, dvdd, avdd, gnd) and gate signal.


▲ GVDD

▲ GND

▲ Low side gate

3. The output of the fault pin is toggled with noise when the load is applied.

 

How can we solve the problem?

  • 0
    TI__Guru 65420 points
    Joanne,

    Could you please provide the layout as well?

    Regards,

    -Adam
  • 0 in reply to Adam Sidelsky
    Prodigy 20 points

    Adam,

    Thanks for your reply.

    Here is the layout.

    Regards,

    Joanne.

    DRV8302_EVM.pdf

  • 0 in reply to joanne yoon
    TI__Guru 65420 points
    Joanne,

    Your main VDRAIN (PVDD) bulk caps seem a little small (4 of 6.8uF), Have you tried increasing the capacitance here?

    There are many more vias connecting the PVDD plane to the high side FETs but much fewer vias connecting the bulk caps to the plane input, I'm not sure if there are enough Vias on the input to the PVDD plane to carry the current that is needed by the FETs.

    You can check this by checking the voltage difference between the board power supply input and the drain of the highside FETs while the motor is loaded. There should be little to no voltage difference if the board design is adequate.

    What trace width are you using for all GHx and SHx? These should be thicker to ensure that these signals can be adequately monitored by the DRV.

    In general vias are not recommended in the SHx or GHx paths.

    Where are your motor connections? I don't see a connector or through hole on the SHx nodes.

    Regards,

    -Adam