Proper Plane Design Techniques

Estimated reading time: 2 minutes

Continuing our discussion from the November issue of Design007 Magazine on proper plane design, Kris Moyer, an instructor for the Global Electronics Association, shares techniques he teaches his PCB design students to use.

Kris, you spend time on plane design in your advanced design classes. What topics do you focus on, and why is plane design so important?

Kris Moyer: When it comes to plane design, there are several challenges with modern high-speed designs. Planes, or more specifically, mirror/return paths, are critical to proper controlled impedance transmission line design. Additionally, to mitigate high-speed switching “noise,” the use of planar capacitance is now necessary and critical. A significant amount of the “noise” seen on the power and return lines of the digital signals is the result of the Vcc/Ground bounce. These bounces, in turn, are typically the result of the parasitic inductance of the digital devices’ Vcc and GND pins.

As a digital signal changes state from 0-1 or 1-0, there is a momentary demand for increased current from the power rails. This demand needs to be supplied during the transition period. The rate at which current can be supplied is dependent on the resistance (R), inductance (L), and capacitance (C) of the component leads, component values, and trace/transmission line impedance.

Due to the ever-increasing speed/decreasing time of the digital transition, the time delay of the R/L/C of the leads/devices is greater than the total transition time. This means that the classic method of adding a capacitor to the power pins of the digital devices is no longer effective for this instantaneous switching current. This is primarily due to the parasitic inductance (L) of the device leads, and the total capacitance of the power supply must still be considered in the design; therefore, physical capacitors must be included in the design. A capacitor made from a pair of planes, either using dedicated embedded capacitance material or standard PCB material, is the only device in the design with sufficiently low parasitic inductance to respond quickly enough to meet this new, extremely fast switching current demand.

To continue reading this article, which originally appeared in the January 2026 issue of I-Connect007 Magazine, click here.