DRV8300: Protecting the gates from excessive Vgs

Tomer Bruchiel

Intellectual 640 points

Part Number: DRV8300

Tool/software:

Hello,

We am using the DRV8300D for one of our projects.

This project is working and already in production but we are have issues somethings with the motors.

There are zener diodes between the SHx and GHx and between the ground to the GLx.

The ones between the ground to the GLx.are non issue but it occurred to me that ones between the SHx and GHx can become forwarded biasd and conduct from the SHx (from the motor phase essentially) to the GHx when GLx is on anf GHx is off.

Is that a problem?

Should I remove it or place a TVS instead? Is it even required to protect the MOSFETs gates? I remember seeing it on the evm board.

The motors are powered by a 16V supply but the Back EMF can be higher.

The DRV8300D is powered by a regulated 12V supply.

Attached is the section of the circuit in question.

Thanks,

Tomer

9 months ago

0 Joshua Maize 9 months ago

TI__Genius 12231 points

Hi Tomer,

Thank you for reaching out.

Can you help to measure the GHx-SHX voltages when these diodes begin to conduct? My concern would be that we have an absolute max spec for GHx-SHX of >-0.3V, and if this differential voltage is large we can run into damage on the outputs.

Best Regards,

-Joshua

0 Tomer Bruchiel 9 months ago in reply to Joshua Maize

Intellectual 640 points

Hi Joshua,

I cannot measure it at the moment, all my systems are on the fields and the next batch is scheduled for next month.

I would like to understand that earlier.

This is a recommendation that comes form the EVM.

See link below and attached file.

https://www.ti.com/tool/DRV8300DIPW-EVM#design-files

MD029A(001)_Sch.PDF

If this is not required, I can remove it.

If it is required and is non issue, I will leave it.

If it is required but may pose a danger, I can replace it with a bi-directional TVS (if possible).

Please advise.

Thanks,

Tomer

0 Joshua Maize 9 months ago in reply to Tomer Bruchiel

TI__Genius 12231 points

Hi Tomer,

Thank you for the response.

The included zener diodes are not absolutely necessary for design but are useful as transients clamps, and so they are included in the EVM as such.

From.my understanding and the behavior you have mentioned i do not see an issue as long as the voltages/voltage differentials are within the abs-max defined in the core IC datasheet.

Hope this information helps.

Best Regards,

-Joshua

0 Tomer Bruchiel 9 months ago in reply to Joshua Maize

Intellectual 640 points

Will it be a good idea to replace them with bi-directional TVS diodes?

0 Joshua Maize 9 months ago in reply to Tomer Bruchiel

TI__Genius 12231 points

Hi Tomer,

No i don't believe that would be helpful for your case and you can leave the design as in.

Best Regards,

-Joshua

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DRV8300: Protecting the gates from excessive Vgs