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26 DESIGN007 MAGAZINE I NOVEMBER 2025 • The high number of supplies leads to higher- layer-count substrates. • Because digital circuits typically share a com- mon ground reference, there is no justification for splitting the ground plane. • Splitting the ground plane introduces imped- ance discontinuities, increases crosstalk, and exacerbates EMI. • To minimize stubs and reflections, designers should employ back-drilled vias, via-in-pad structures, and blind or buried vias. • The multiplane HDI stackup typically incorpo- rates 5th-order HDI structures, embedded capacitance, and multiple tightly coupled ground-power pairs. • Copper pours and multiple thermal vias must be precisely aligned with the GPU die and voltage regulator module (VRM) regions to facilitate efficient heat dissipation. • The real challenge lies in achieving micro-ohm AC impedance across the power delivery network. DESIGN007 B E YO N D D ES I G N Resources • Beyond Design by Barry Olney: "PDN Trends and Challenges, Plane Crazy Part 2," "The Fundamental Rules of High-Speed PCB Design Part 3." • Tuning and Deploying a Language Model on NVIDIA H100 • NVIDIA H100 Tensor Core GPU Architecture • Designing hardware for hosting AI-tailored GPUs Barry Olney is managing director of In-Circuit Design Pty Ltd (iCD), Australia, a PCB design service bureau that specializes in board- level simulation. The com- pany developed the iCD Design Integrity software, incorporating the iCD Stackup, PDN, and CPW Planner. You can download the software at www.icd.com.au. To read past columns, click here. BOOK EXCERPT The Printed Circuit Designer's Guide to... Designing for Reality by Matt Stevenson, ASC Sunstone Circuits Chapter 8: Advice for Designers Designing for reality doesn't have to be daunting or a hassle. It takes time to gain a detailed working knowl- edge of each production component. If you make a point of working with patient, reliable, and trustwor- thy manufacturing partners, you can have great suc- cess as you learn. While you work to grow more familiar with the various elements of produc- tion like metallization and imaging, keep these ideas in mind, especially as your designs become more complex. Component Placement Is an Art and a Science To the uninitiated, PCB design may seem like a rigid, by-the-book process. It's not. We urge you to always be study- ing the craft of PCB design rather than just memorizing and replicating basic skills. We rec- ognize that PCB design is a world filled with limits, tol- erances, and parameters, but don't let that stop you from being ative. Placement of components is where art and science converge. Though there is no single right way to per- form this task, the orientation, place- ment, and organization of your compo- nents will influence the manufacturabil- ity of design. To consistently create highly function- al and manufacturable designs, you'll need to become a true craftsperson. It's an ongoing process, one that requires a lot of practice, understanding of how your CAD tool functions, and manufac- turing partners that will collaborate with you and help you improve your designs. Continue reading...