DRV8328AEVM: DRV8328A

William Szatkiewicz

Part Number: DRV8328AEVM
Other Parts Discussed in Thread: DRV8328

Hi,

Do you have any application schematic examples of a 3 phase PMSM motor control with the DRV8328A? My question is to review a working schematic and compare it to mine. One concern is the LSS pin of the DRV8328A. I do not have bus current sensing but individual current sensing off of each phase. Is it okay to use only one phase for the LSS pin? How has TI done it?

Here is a screenshot of my schematic for review.

Any help or suggestions would be appreciated.

Thank you,

William

over 2 years ago

0 Andrew Liu over 2 years ago

TI__Mastermind 18916 points

Hi William,

Hoping this FAQ may be helpful regarding your LSS pin handling of current sensing scheme

link: https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1130163/faq-drv8328-implementing-3-external-csas-using-drv8328
the DRV8328 device only has one LSS pin, so it's optimized for using only one external shunt resistor and CSA

Elaborating on schematic examples,

the diagrams I would refer to are either the official DRV8328EVM schematic or DRV8329EVM schematic
- link: https://www.ti.com/tool/DRV8328AEVM
- link: https://www.ti.com/tool/DRV8329AEVM

Best Regards,
Andrew

0 William Szatkiewicz over 2 years ago in reply to Andrew Liu

Prodigy 120 points

Hi Andrew,

Thank you for the response and information.

So, is it not recommended to use one of the three phases sense resistors to the LSS pin (shown below), as opposed to completely disabling the overcurrent protection as explained in the FAQ you sent?

Thank you,

William

0 Akshay Rajeev Menon over 2 years ago in reply to William Szatkiewicz

TI__Mastermind 19866 points

Hey William,

I will aim to provide a response before the end of the week.

best Regards,

Akshay

0 William Szatkiewicz over 2 years ago in reply to Akshay Rajeev Menon

Prodigy 120 points

Hi Akshay,

Thank you, I look forward to your response.

Best regards,

William

0 Akshay Rajeev Menon over 2 years ago in reply to William Szatkiewicz

TI__Mastermind 19866 points

Hey William,

If you are using 3 external CSAs then LSS is tied to GND so VsenOCP is disabled.

We cannot connect it in the arrangement proposed as then phase B and C won’t get a connection to LSS. And LSS is required for the low side gate drive sink current. So, if the LSS connection for phase B and C is removed then you will never be able to turn off the low-side MOSFET.

Hope this offers some clarification.

Best Regards,

Akshay

0 William Szatkiewicz over 2 years ago in reply to Akshay Rajeev Menon

Prodigy 120 points

Hi Akshay,

Won't phase-B and Phase-C still be connected to LSS through the low impedance of the current sense resistor? Isn't that enough to enable the DRV8328 to turn off the MOSFET referenced to LSS through the low impedance current sense resistor of the phase?

Thank you,

William

0 Akshay Rajeev Menon over 2 years ago in reply to William Szatkiewicz

TI__Mastermind 19866 points

Hey William,

I will aim to provide a response before the end of the week.

Best Regards,

Akshay

0 Akshay Rajeev Menon over 2 years ago in reply to Akshay Rajeev Menon

TI__Mastermind 19866 points

Hey William,

If you remove the crossed-out wire then there is no connection between the LSS and phase B and C. Since there is only one LSS pin we can’t have the LSS be connected to the high side node of each shunt separately. As the E2E FAQ mentioned having three external CSA will result in the VsenOCP being diabled.

Hope this offers some clarification.

Best Regards,

Akshay

0 William Szatkiewicz over 2 years ago in reply to Akshay Rajeev Menon

Prodigy 120 points

Yes, thank you.

+1 Akshay Rajeev Menon over 2 years ago in reply to William Szatkiewicz

TI__Mastermind 19866 points

You are welcome!

If this has resolved your issue then please mark the answer as "resolved".

Best Regards,

Akshay

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DRV8328AEVM: DRV8328A