USB-C Wi-Fi/BLE Environmental Sensor Node
Purpose
Consumer low-power environmental sensor node powered from USB-C 5 V default sources. Measures temperature and relative humidity with a digital I²C sensor and reports over 2.4 GHz Wi-Fi/BLE.
Implemented Architecture
- USB-C receptacle: J1 UJ20-C-H-G-SMT-2-P16-TR, 5 V default sink.
- CC termination: R1/R2 5.1 kΩ Rd pulldowns on CC1/CC2.
- Input protection: U3 TPS25940LRVCR eFuse for reverse-current blocking, OVP, UVLO, and OCP planning for 0.5–3 A USB sources.
- Regulation: U4 MP28301GG-P low-Iq buck regulator, protected 5 V to 3.3 V.
- Wireless MCU: U1 ESP32-C6-WROOM-1-N8 module, 2.4 GHz Wi-Fi + BLE 5.x class radio module.
- Sensor: U2 SHT41-AD1B-R3 I²C temperature/RH sensor.
- I²C: SDA on ESP32-C6 IO6, SCL on IO7, both pulled up to 3.3 V with 10 kΩ.
Main Nets
- USB_VBUS: raw USB-C 5 V input, max current metadata 3 A.
- 5V_PROTECTED: eFuse output to buck regulator, max current metadata 3 A.
- 3V3: regulated system rail, max current metadata 0.7 A.
- GND: common ground.
- I2C_SDA / I2C_SCL: low-speed digital sensor bus.
Power Budget Planning
Approximate design target: ESP32-C6 Wi-Fi transmit peaks up to several hundred mA, sensor draw negligible versus radio, regulator selected with 700 mA class output to cover radio bursts. eFuse current limit should be configured during detailed datasheet tuning for the intended product current limit: conservative consumer default around 0.5–1 A, or higher up to 3 A if thermals/connector/source assumptions support it.
Items Requiring Datasheet-Level Tuning Before Layout/Release
- TPS25940L ILIM, UVLO/OVP, dV/dt, PGOOD/FLT usage, and thermal dissipation values.
- MP28301 output voltage feedback/configuration, required inductor value/current rating, input/output capacitor ESR/capacitance, and layout-critical switching loop.
- ESP32-C6 module boot strapping, EN/reset behavior, optional UART programming pads, and antenna keepout.
- Confirm exact module regulatory certifications for target SKU and sales regions.
Validation Performed
Electrical rule check subset for floating pins, no-connects, power pins, undriven nets, and single-pin nets reports no ERROR/WARNING/UNCERTAIN items after marking spare GPIOs intentionally unused.