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Motherboard Carrier — Schematic Notes
Doc No. HW-MB-014 · Rev D · Confidential · Do not distribute
Power tree: ATX 12V → buck 5V/3V3 → LDO rails. PCIe diff pairs length-matched.
Keep crystal within 5 mm of SoC. USB ESD at connector.
| Net | Source | Sinks | Notes |
|---|
| VCC_3V3 | U12.OUT | SoC, DRAM, PHYs | 100 nF per rail |
| GND | — | plane | via stitch |
| PCIE_TX_P/N | SoC | SLOT1 | 85 Ω diff |
| USB_DP/DM | J_USB | HUB | 90 Ω diff |
| DDR_DQ[0..63] | SoC | U_DRAM | fly-by |
12V_ATX
│
[Buck 5V]──[Buck 3V3]── SoC / DRAM
│
[LDO 1V8]── Analog
Layout checklist: (1) crystal keep-out (2) USB ESD (3) via-in-pad review (4) silk clear of pads.