PCB Design and Layout — Wolfspeed Power Applications Forum

[FAQ-PCB-3] Do SiC MOSFETs generate a lot of noise?

TBhatia — Wed, 01 Feb 2023 16:32:44 +0000

Yes. SiC devices do generate higher noise than Si due to its faster switching. But if you follow good design principles of high speed switching circuit layout, you can have successful SiC based PCB design. Much of the "noise" in the circuit is due to parasitic elements in the layout that can cause increased ringing and unintended coupling of high dv/dt nodes into other parts of the circuit. Reducing these parasitic elements is key to reducing noise and EMI.

For examples of good layout practices, be sure to check out Wolfspeed's reference webpage. All reference and evaluation boards provide good layout examples for a variety of packages and applications. For additional support, please contact Wolfspeed Field Application Engineers.

[FAQ-PCB-2] Are there any special considerations for PCB layout when using SiC MOSFETs?

TBhatia — Wed, 01 Feb 2023 16:18:19 +0000

Care is needed for PCB layout when using SiC MOSFETs just like using Si MOSFETs in switching power supplies. Some best practices are listed below:

• Minimize the loop inductance of gate drive circuit

• Use the shortest leads possible for through-hole devices to minimize parasitic inductance

• Avoid overlapping of gate and drain traces to minimize Cgd and cross talk in hard switching bridge circuits

• Minimize common source inductance to prevent slowing down gate drive and gate oscillation for 3-lead devices. This can be done by making a kelvin connection where the device terminal meets the board. The gate drive circuit should connect to the source lead separately from the power path, and the gate drive circuit should not overlap the power circuit. Packages with kelvin source connections for the gate drive make it easier to separate these circuits on the PCB, and also improves switching speed.

• Use low inductance DC bus configurations. Using high quality film and/or ceramic capacitors placed as closely to the devices as possible will help to reduce ringing and voltage overshoot at turn-off. The DC bus should use overlapping pours in a PCB or laminated bus structures when working with modules.

Please refer to the full Application note PCB LAYOUT TECHNIQUES FOR DISCRETE SiC MOSFETs for detailed design considerations and tips for a good layout using discrete SiC MOSFETs.

[FAQ-PCB-1] What tools does Wolfspeed provide for PCB and mechanical design?

TBhatia — Wed, 01 Feb 2023 16:08:52 +0000

Wolfspeed provides ECAD models for Altium, OrCAD, KiCAD, and Eagle formats for all discrete SiC MOSFETs and diodes directly on Wolfspeed.com in the product tables for individual parts, or you can download the entire library from the Tools & Support page. 3D STEP files are also available for all discrete and power module products. Additionally, ECAD models are available in other formats through ultralibrarian.com, and are built into the Altium Manufacturer Part Search tool.

PCB design files for all the reference designs are also available for download on the reference design product page under "Technical & sales Documents" section of the page.