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KiCad STM32 Reference Design v1 (4-Layer)

Production-quality 4-layer reference design around an STM32G474 (Cortex-M4F @ 170MHz). Built to land cleanly on a small JLCPCB / OSH Park run with no spin. Use as a starting point for a CAN-FD industrial board, a robot peripheral, or a USB-C-powered measurement front-end.

Block diagram

USB-C(20V cap, 5V PD-trigger fallback)
      │
      ▼
  TPS62120 buck → 3V3_DIG
                 │
  AP7115 LDO ← 3V3_ANA  (clean for VDDA)
                 │
                 ▼
            STM32G474RE
            ├── SWD header (10-pin Cortex-M)
            ├── USART1 (UART debug)
            ├── USART2 (UART app)
            ├── CAN-FD #1 (MCP2562FD)
            ├── CAN-FD #2 (MCP2562FD)
            ├── SPI1 → ICM-42688-P IMU
            ├── I2C1 → reserved expansion header
            └── 8-pin user GPIO header

What's in this repo

File	Purpose
stm32_ref.kicad_pro	KiCad project file
stm32_ref.kicad_sch	Top-level schematic (S-expression text)
stm32_ref-power.kicad_sch	Power-tree subsheet
design-rules.kicad_dru	Manufacturing-class design rules (JLCPCB 6/6 mil, ≥0.2mm hole)
stackup.md	Layer stackup with controlled-impedance values
bom.csv	Pre-checked BOM with LCSC + Digikey part numbers
assembly-notes.md	Reflow profile, panelization notes, fiducials

The .kicad_pcb file is not bundled. Reference designs ship as electrical intent — the PCB layout decisions belong to your form factor, not ours. The schematic + DRU + stackup files give you a one-click starting point in KiCad.

Design choices worth knowing

Power tree

USB-C VBUS feeds a wide-input buck (TPS62120) down to 3.3V digital. The analog rail is a separate LDO (AP7115) from the same buck output so VDDA stays clean during digital switching. Bulk caps: 10µF + 100nF every supply rail at every IC.

The PD trigger is a fallback path — if you connect to a USB-C PD source, an attached IP2721 controller can request 9V to drive higher-power peripherals on a future revision. For default 5V-only operation, leave that footprint unstuffed.

CAN-FD

Two MCP2562FD transceivers on FDCAN1 and FDCAN2. Common-mode chokes at both bus ports (TDK ACT45L-220-2P-TL00, 220µH/100mA). Bus termination as DNP — populate on the boards at the bus ends.

Crystal

8 MHz on HSE with 12pF load caps (calculated for an Abracon ABM3-8.000MHZ-D2Y-T crystal, 6pF CL, 4pF stray). Verify load caps if you substitute a different crystal — see assembly-notes.md for the formula.

License

MIT. Use freely in commercial designs — no attribution required, though we always appreciate a tweet if it lands you somewhere good.