Issue link: https://iconnect007.uberflip.com/i/1535183
From data centers to smartphones, design- ers know that the ohms have it. Getting imped- ance right ensures all-important signal integ- rity and delivers high-performing boards. Our designers understand the importance of con- trolled impedance, but not everyone addresses it in their designs. e most common and important controlled impedance types we see include microstrip, stripline, embedded microstrip, and differential pairs. • Microstrip: e most used form of con- trolled impedance because it is easy to design and cost-effective. It creates a transmission line using a signal trace on one side of a dielectric layer and a ground plane on the other. Designers can adjust the width and thickness of the trace and the thickness of the dielectric layer to achieve a specific controlled impedance. • Stripline: A PCB trace with a signal path routed on an internal layer and propagated Proactive Controlled Impedance Connect the Dots by Matt Stevenson, ASC SUNSTONE CIRCUITS between two ground planes. To achieve controlled impedance throughout the entire length of the trace, designers need to calculate the width of the signal trace, thickness of the material between layers, and the distance between the signal trace and ground planes. • Embedded microstrip: Transmission lines have a signal trace inside the PCB's dielectric, placed between two layers. To achieve controlled impedance, designers must calculate the trace width, spacing, and dielectric thicknesses of the surround- ing material. • Differential pairs: Two traces on a board that carry equal but opposite signals. Trace width, spacing, copper thickness, and other factors influence impedance. We recommend designers specify controlled impedance signals for differential pairs in the schematic. 52 DESIGN007 MAGAZINE I MAY 2025