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UCC5390: Challenges with non-isolated gate drivers for low side circuitry

Lahiru Ambegoda
Prodigy 20 points
Part Number: UCC5390


Hi,

I am studying on isolated and non-isolated gate drivers for IGBT driven motor drive applications. My application area is three-phase two-level motor drives. I can understand that using all 6 switches with isolated gate drivers is obviously good. I am considering to use non-isolated gate drivers for low side circuitry and I believe there might be challenges with that approach therefore, I am exploring about it. The part number (UCC5390) and datasheet title of the isolated gate driver currently in use is "UCC53x0 Single-Channel Isolated Gate Driver". I would appreciate if you could provide more information regarding my query and if you suggest a product I can look into more details of it.

Thank you.

Best Regards,
Lahiru Ambegoda.ucc5390.pdf

  • 0
    TI__Expert 6730 points

    Hi Lahiru, 

    Our expert on this device is currently out of office for the Thanksgiving holiday. Please expect a response early next week when we are back in office. Thank you! 

    Vivian

  • 0
    TI__Prodigy 160 points

    Hi Lahiru, 

    Thank you for reaching out.  I wanted to clarify if you needed additional information on UCC5390 for this type of motor drive application? Or if you are looking to replace UCC5390 with a non-isolated device?  

    If you are currently using UCC5390 for your system, would it be possible to see a schematic or system layout? 

    Kind regards, 

    Abbie 

  • 0 in reply to Abbie Ortega
    Prodigy 20 points

    Dear Abbie,

    Thank you for your reply. I am looking to replace UCC5390 with a non-isolated gate driver for low-side circuitry. I would like to study the phenomenon and identify the pros and cons of this matter.

    Unfortunately, I do not have rights to share the schematic diagrams at the moment. I will try to give as much as information I can.

    Thank you,

    Best Regards,
    Lahiru Ambegoda.

  • 0 in reply to Lahiru Ambegoda
    TI__Mastermind 23226 points

    Hi Lahiru,

    You should be able to replace the low side driver with a non-isolated gate driver, and tie the high voltage and low voltage grounds together. The circuit will still work. However, there are usually safety requirements and certifications that forbid that the grounds be tied together. The concern is that the low side switch could be damaged, and connect high voltage to the gate driver output, and that high voltage could make it back to the low voltage side and damage components or create a hazard.

    Best regards,

    Sean

  • 0 in reply to Sean Cashin
    Prodigy 20 points

    Hi Sean,

    Thank you for coming-up with these problems. Will there be electromagnetic interferences (EMI) towards gate driver and the controller when working with non-isolated gate driver?  Kindly provide if you have TI's application note or other document that supports your statement.

    Thank you,

    Best Regards,
    Lahiru Ambegoda.  

  • +1 in reply to Lahiru Ambegoda
    TI__Mastermind 23226 points

    Hi Lahiru,

    Here is a document that discusses "functional" isolation, or the minimum isolation required for a circuit to work: https://www.ti.com/lit/wp/slyy204b/slyy204b.pdf

    If there is lots of switch node ringing, it will indeed couple to other parts of the circuit if you use a non-isolated driver. However, if you use the same ground plane for the whole board, the turn off ringing will be a lot lower than if you have a smaller HV- rail. Still, if you share the same logic ground and power ground, you will have to pay more attention to ground bounce than if you use an isolated gate driver. 

    Non-isolated gate drivers will be cheaper, but an isolated gate driver on the low side does indeed help keep any EMI caused by gate resonance out of the low voltage side of the board. 

    Best regards,

    Sean