DRV8305: Ringing/oscillation on MOSFET gate.

Bruno Duan

Part Number: DRV8305

Hi Ti team,

We are using DRV8305 gate driver to finish a BLDC driver. We found really heavy oscillation on the MOSFET gate. we are using MOSFET: IPB042N10N3, no gate resistor, driving current set 100mA ON 200mA OFF, shown in below pictrue. You could see the negative spike is around -9.2V. I have questions below:

1. I only found this oscillation when bus current is big(like start up or with a heavy load), when the motor in free speed run(current around 3A), we did not see that. why? what caused the oscillation?

2. the Negative spike is -9.2V, duration is below 34ns, will it be a risk to damage the DRV?

3. Any suggestion to improve the oscillation? Add gs capacitor?

Thanks!

Best regards,

Bruno Duan

over 4 years ago

0 Adam Sidelsky over 4 years ago

TI__Guru 63350 points

Bruno,

Thanks for posting on the MD forum!

Is this waveform the high side gate? Or low side gate?

Can you share your schematic and layout?

Regards,

-Adam

0 Bruno Duan over 4 years ago in reply to Adam Sidelsky

Prodigy 225 points

Adam,

Thanks for your reply!

Above picture are from high side gate, Low side gate also have ringing but better than the high side. see below picture:

I alreday submit a request to add u as a friend.

Best regards,

Bruno Duan

0 Adam Sidelsky over 4 years ago in reply to Bruno Duan

TI__Guru 63350 points

Bruno,

I have approved your request, please send the files privately.

Regards,

-Adam

0 Bruno Duan over 4 years ago in reply to Adam Sidelsky

Prodigy 225 points

Adam,

I have already sent the files to you. plese help to review. Thanks!

During my latest test, I found a strange wave form. As shown below, we added 39ohm gate resistor and 4.7nF Cgs to improve ringing issue, we could see improvment at 3rd picture. when we check the wave form at gate driver side to make sure voltages in spec. found the first wave form, at beging of the signal turn to ON, there have a 15.7V plateau as we know the output driving voltage is around 10V. I checked low side driving wave form also, it is not like the high side, so I want ask:

1. why this will happen?

2. we could see the voltage is near to 16V which is the AB rating for those two pin, will it damge DRV when it reach 16V?