Component and layout rules for USB-C, PD, and CMTI

Over the last two months, we mapped out how USB-C, Power Delivery (PD), vehicle-to-load (V2L), and high common-mode transit immunity (CMTI) are reshaping the landscapes of test and measurement and electric vehicles (EVs). The next challenge is practical: how do you translate those high-level architectural requirements into a schematic that works and a PCB layout that passes?

This post delivers the essential design clues—the component choices, layout constraints, and rule-of-thumb practices—that bridge concept to copper. It’s about moving from theory to implementation, giving engineers the confidence to build USB-C and PD systems that meet compliance while surviving real-world stress.

Designing for high CMTI: Turning ratings into real layout rules

To maintain high CMTI on a real board, the isolation barrier is non-negotiable. Specialized digital isolators—either capacitive-based or magnetic-based—are engineered to withstand the brutal transient voltage spikes in the range of kV/