ESP32 Low-Power Circuit Design

flux

Work completed
  • Components added:
  • Nets wired:
    • SPI (MOSI/MISO/SCK/CS) and IRQ between ESP32-S3 and RFM95W
    • RF output → PI-match → antenna-select circuit
    • USB D+/D− through 27 Ω series resistors to USB4105 data pins; CC1/CC2 through pull-downs; VBUS through TVS to charger VIN
    • Battery → protection → buck regulator → 3.3 V rail → ESP32-S3 and load-switch inputs
    • Load-switch enables driven by ESP32-S3 GPIOs
    • I2C pull-ups tied to 3.3 V rail and SDA/SCL
    • ESP32-S3 BOOT/EN/UART lines to debug header
Tasks not completed or requiring your action
  • Add the USB-C receptacle footprint (we can’t place that automatically)
  • Connect ESP32-S3 EN pin to the debug header EN pin
  • Connect the RF ESD diode input to the selectable antenna circuit output
  • Connect the USB-C VBUS pins to the battery/charger power net
  • Fetch and review ERC/DRC results using the @review tool
Success criteria status
  • All components are present and most nets are wired—but the USB-C footprint and several critical connections remain incomplete.
  • ERC/DRC have not yet been run; we cannot confirm the design fully passes rules checks.
  • RF matching network and power management appear correct except for missing ESD diode routing and VBUS net.
Recommended next step Please add the USB-C connector footprint and complete the remaining connections (EN pin, RF ESD diode, VBUS net), then run ERC/DRC. Once the schematic is error-free, we can proceed to PCB layout.
U2 ANT - L1 P1
U2 ANT - L1 P1
J1 VBUS - D3 1
U1 IO20 - R3 P1
U3 FB/VO - U1 3V3
R4 P2 - J1 DN1
U2 DIO0 - U1 IO26
R4 P2 - J1 DN1
U3 FB/VO - U1 3V3
U2 ANT - L1 P1
U2 MOSI - U1 IO13
U4 SET - U1 IO17
U5 SET - U1 IO18
J1 CC2 - R2 P1
U1 IO20 - R3 P1
R3 P2 - J1 DP1
U4 SET - U1 IO17
U3 FB/VO - U1 3V3
U5 SET - U1 IO18
R4 P2 - J1 DN1
U6 SET - U1 IO21
U2 MOSI - U1 IO13
U1 IO19 - R4 P1
R3 P2 - J1 DP1
U2 DIO0 - U1 IO26
U6 SET - U1 IO21
U2 MISO - U1 IO12
U3 FB/VO - U1 3V3
U3 FB/VO - U1 3V3
U2 MISO - U1 IO12
J1 VBUS - D3 1
U1 IO19 - R4 P1
U3 FB/VO - U1 3V3
J1 CC2 - R2 P1
U3 FB/VO - U1 3V3
U2 NSS - U1 IO15
U2 SCK - U1 IO14
U2 SCK - U1 IO14
R3 P2 - J1 DP1
J1 VBUS - D3 1
U2 NSS - U1 IO15
C4
Capacitance
100nF
U2
D2
R6
Resistance
4.7kΩ
C3
Capacitance
100nF
C2
Capacitance
1.8pF
R2
Resistance
51kΩ
L1
Inductance
15nH
U5
R5
Resistance
4.7kΩ
U4
R1
Resistance
51kΩ
R4
Resistance
27 Ω
U6
C1
Capacitance
1.8pF
R3
Resistance
27 Ω
D1
J1
GND
J2
U1
U3
D3

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    Architectural Lavender Translation Collar thumbnail
    Architectural Lavender Translation Collar – ESP32‑S3 Wi‑Fi + LoRa, USB‑C, Li‑ion, low‑power design
    Overview Experience a cutting-edge IoT solution with this low‑power board built around the ESP32‑S3‑MINI‑1‑N8. Designed for seamless Wi‑Fi (2.4 GHz), BLE, and LoRa (868 MHz) connectivity, this board integrates ENS161 and ENS210 sensors over I2C alongside an RFM95W‑868 LoRa radio on SPI. It is powered via a 3.7 V Li‑ion cell with USB‑C charging up to 500 mA, complete with full battery protection, a robust 3.3 V rail tailored for Wi‑Fi burst currents, and per‑peripheral power gating to enhance energy efficiency.
    Core Features • MCU: ESP32‑S3‑MINI‑1‑N8 equipped with an onboard PCB antenna for 2.4 GHz Wi‑Fi/BLE, ensuring optimal wireless performance. • Sensors: Integrated ENS161 and ENS210 sensors utilize a shared I2C bus with controllable 4.7 kΩ pull‑ups for streamlined communication. • LoRa Radio: The RFM95W‑868 module, connected via SPI, enables long‑range communication at 868 MHz.
    Power & USB‑C Connectivity • Battery: A reliable 3.7 V 1200 mAh Li‑ion battery connected via a right‑angle JST‑PH 2‑pin connector features built‑in battery protection. • Charging: The USB‑C receptacle, with CC resistors and TVS protection on D+/D− along with series resistors, supports fast, safe charging with a current limit of 500 mA. • Regulation: A dedicated 3.3 V regulator capable of handling Wi‑Fi burst currents coupled with bulk and high‑frequency decoupling ensures stable operation, supported by status LEDs indicating power and charge states.
    Low‑Power Control • Peripheral Management: Load switches allow selective power‑gating of the ENS161, ENS210, and RFM95W modules, controlled directly by ESP32‑S3 GPIOs. • Energy Efficiency: Controllable I2C pull‑ups minimize idle current, vital for prolonged battery life in IoT applications.
    RF and Antenna Integration • 2.4 GHz: Utilizes the integrated PCB antenna on the ESP32‑S3 with proper ground/metal keep‑out zones for optimal signal integrity. • 868 MHz: Features a controlled‑impedance feed from the RFM95W to a PI matching network (C‑L‑C pads) with flexible antenna options—selectable via SMA connector, chip antenna, or PCB trace—and includes RF ESD protection.
    Connectivity & Debug Features • USB‑C Interface: Provides secure data connectivity with integrated safeguards and proper terminations. • Debugging: A comprehensive programming/debug header exposes EN, BOOT, and UART lines, with test points on key rails and buses (3V3, VBAT, SCK, MOSI, MISO, SDA, SCL, RESET/EN, GND) to simplify development and troubleshooting.
    Design Verification • Rigorous ERC/DRC and decoupling checks ensure adherence to component ratings and optimal signal routing. • Maintain RF keep‑outs and impedance‑controlled traces for both 2.4 GHz and 868 MHz paths, securing reliable performance even during high‑intensity operations.
    #IoT #ESP32S3 #LoRa #LowPowerDesign #USB-C #WirelessConnectivity #BatteryPowered #RFDesign

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