The official acts as a reference design, showing how to break out the high-density connectors of the CM4 into usable interfaces like USB, HDMI, Ethernet, and PCIe.

Many companies design compact or specialized boards for the CM4 to fit specific use cases like routers, industrial automation, or mini-PCs.

A common rule of thumb: place a 0.1 µF capacitor within 2 mm of each power pin of the CM4 and each connector.

| Block | Critical Details | |-------|------------------| | | 5V @ 2.5A+ (peak), good decoupling (100nF + 10µF near each CM4 power pin). Use PMIC like DA9061 or MPM3630 . | | HDMI | ESD protection (e.g., USBLC6-2 ). Keep differential pairs <2mm length mismatch. | | USB 2.0 | 22Ω series resistors, common-mode choke (optional but wise). | | PCIe (if used) | AC coupling caps (0.1µF) on TX lanes, reference clock routing. | | MIPI DSI/CSI | Strict impedance control (100Ω diff). Length matching within 0.5mm. | | SD Card (if on carrier) | Pull-ups on CD/DAT3, series resistors on CMD/CLK. | | ETH (if using CM4’s PHY) | Magnetics with center tap decoupling. |