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UCC27282: complete GND plane or separated GND plane in Motor drive PCB design?

Yonghui zhu
Intellectual 430 points
Part Number: UCC27282
Other Parts Discussed in Thread: UCC27201A-Q1

Hi Expert, 

For high power 48V BLDC driver(about 500W or more) design (usually for Robotics appliation). Because it's non-isolation design, we often face a dilemma that we need to keep a complete ground plane or separate the signal ground (GND) from inverter power ground (PGND). GND and PGND need to be connected together finally because of non-isolation design. 

The traditional saying is that GND and PGND need to be separated, then single connection in power input, which can isolate the noise from high power PGND to GND because of PGND is large current. But there are still some signal interconnections between GND and PGND,  such as gate driver siganls, current sample signals. They need to cross between two separate planes

so how about keeping a complete ground plane for both GND and PGND? In motor driver design, usually there are several ground planes for large current. Keeping a complete ground plane means a lowest impedance plane for all components. Also it will be a good path for thermal conduction.  The PCB layout will be much simpler. Inverter related power components will be kept in same area.

What's the best practice for control ground (GND) and inverter PGND in non-isolation motor driver PCB design?

Thanks

Peter 

  • 0
    TI__Expert 8315 points

    Hey Peter,

    Thanks for your question regarding UCC27282.

    For your application, it seems that a good reference design for this is the Automotive 1-kW 48-V BLDC Motor Drive Reference Design.

    This is a 1-kW system and utilizes the UCC27201A-Q1 as opposed to the 500W system and UCC27282 that you are utilizing but will operate very similar. As for the ground references for this. The low-side FET as well as VSS are connected to the same ground plane of GND_B here.

    Let me know if you have any questions.

    Thank you,

    William Moore

  • 0 in reply to William Moore
    Intellectual 430 points

    Hi William

    Thanks for quick response.  This is a good reference. I saw a complete GND_B plane. But the solution is different because MCU board is a daughter card, which means GND_B plane has been physically separated from MCU ground (GND). If the MCU is onboard design, can MCU GND share the same GND_B plane? 

    This is a very critical question for us. it will affect all of our future motor drive design.

    Thanks

    Peter

  • 0 in reply to Yonghui zhu
    TI__Expert 8315 points

    Hey Peter,

    It is generally recommended to keep the powertrain ground and the control signal ground separate. The control signal is better off on a quiet ground due to the noise from the high current power ground. It is possible to utilize the same ground plane if it is sufficiently sized to reduce the noise and parasitic inductances.

    Let me know if you have any further questions.

    Thank you,

    William Moore