- The PDF is the schematic, and the Gerber files can be opened in most Gerber viewers to see the fabrication outputs for the board. The CM5 Carrier is a 4-layer PCB. It is the motherboard for the Linux Mini PC and it is the PCB that I designed for the project. The 3D design files for the chassis/case are uploaded as a separate zip from the Gerber files.
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The board in this project is supposed to be a carrier board for the Raspberry Pi CM5 SoM (Compute Module 5 System on Module). It interfaces the SoM with CSI (Camera Serial Interface) and DSI (Display Serial Interface) connectors, USB 3.0, an SD card slot, and a BQ25895 battery charge management IC with USB-C for power input.
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The high-speed interfaces including CSI, DSI and USB-3 have their differential pairs correctly impedance matched reasonably within 100 ohms and 90 ohms respectively; the board follows JLCPCB's 4-layer JLC04161H-3313 stackup.
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The SD card slot is interfaced with the CM5 connector because I intended to mount "CM5 Lite" SoM onto it (has no onboard storage and requires external storage).
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For the system to be conveniently rechargeable I opted for the TI BQ25895 charge management IC which allowed a connected LiPo battery to be recharged with USB-C. In terms of layout design, surrounding power traces were kept wide with neck down only for IC pins to lower resistance and improve thermals.
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It would be very convenient to have added LED indicators for 5V and 3V3 rails as well as charge status LED indication.
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The chosen 4 layer stackup routes both power and high-speed signals on the top-layer, followed by two internal ground planes, and a bottom routing cleanup layer. Space and routing difficulty could have been saved by reorganizing the component locations and using the 3rd layer as a power plane layer.