A ruggedized, 6-layer High-Density Interconnect (HDI) carrier board designed to commercialize Raspberry Pi CM4 prototypes into deployable industrial AI products. Engineered specifically for high-vibration, noisy environments (agricultural robotics, factory automation) featuring automotive-grade power protection and high-speed PCIe integration.
- Power Delivery Network (PDN):
Wide Input Front-End: 12V/24V nominal input (up to 36V max).
Automotive Protection: Integrated SMAJ24A TVS diode for load-dump transient clamping, and a discrete P-Channel MOSFET (reverse polarity protection) minimizing I2R thermal losses compared to traditional blocking diodes.
Main Rails: Dual highly-efficient synchronous buck converters. TPS5430 (3A) for the 5V main logic rail, and TPS62130 (2A) strategically placed next to the M.2 slot for heavy transient 3.3V AI-accelerator loads. Copper polygon pours utilized for critical thermal dissipation.
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High-Speed Interfaces & Signal Integrity:
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PCIe Gen 2 (5 GT/s): Routed an M.2 Key-M Socket (Lane 0) for NVMe SSDs or Google Coral TPUs. Implemented strictly length-matched, 85Ω differential pairs. Axial pad entries and symmetrical 0.45mm/0.2mm GND stitching vias ensure unbroken low-inductance return paths during Z-axis layer jumps.
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Gigabit Ethernet: RJ45 MagJack with integrated isolation magnetics and correctly biased center-taps for robust 125 MHz differential signaling (100Ω controlled impedance).
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Vision: 22-pin FPC MIPI CSI-2 interface for standard Raspberry Pi cameras.
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6-Layer Stackup: Signal - Solid GND - Power - Solid GND - Solid GND - Signal
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Outer layer copper pours (GND) with strict 3W rule (0.5mm clearance) enforced to prevent coplanar waveguide parasitic capacitance from degrading microstrip differential impedance.
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Designed in KiCad 9.0. DRC zero-error verified.