PCB Design Execution Plan
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Design Notes
Requirements Snapshot
- Board target: 35 mm x 25 mm wearable pod
- Stackup target: 4-layer
- Top: components and signals
- L2: solid GND plane
- L3: 3.3 V plane
- Bottom: signals and antenna traces
- Power target: 500 mAh LiPo, average load about 30 mA, estimated runtime about 16.7 h ideal before derating
- Manufacturing target: JLCPCB assembly with LCSC-sourceable parts where practical
Initial Architecture Decisions
- Use ESP32-C6-MINI-1-N4 as the main wireless MCU.
- Use MAX-M10S-00B as the GNSS receiver with external active/passive antenna via u.FL.
- Use BMI323 on I2C for the IMU.
- Use a simple USB-C 5 V sink with CC pull-down resistors, VBUS TVS, and LiPo charge management.
- Use a low-IQ 3.3 V LDO plus a dedicated load switch to isolate peripherals for deep sleep.
- Use SPI microSD for log storage and optional I2C fuel gauge.
BOM Direction
- USB-C: USB4135-GF-A_REVA
- microSD: 5033981892
- u.FL: U.FL-R-SMT(01)
- Battery connector: S2B-PH-SM4-TB(LF)(SN)
- Optional fuel gauge: LC709203FQH-01TWG
Open Technical Tradeoff
- Very-low-IQ and guaranteed 300 mA+ LDO availability in-library is weak. Likely path:
- choose a compact low-IQ LDO for always-on rail, and
- add a load switch so GNSS, microSD, and sensors can be power-gated.
Finalization Notes
- R1 and R2 updated to 1 kOhm.
- USB-C CC pull-down connectivity remains on the dedicated USB_CC1 and USB_CC2 nets.
- microSD VDD is fed from 3V3_SW through U5, which is the intended switched rail for low sleep current.
- Target layout remains 35 mm x 25 mm, 4-layer, with GNSS RF area requiring a 5 mm keepout discipline around U2 and the antenna path.
Requirements Snapshot
Initial Architecture Decisions
BOM Direction
Open Technical Tradeoff
Finalization Notes
