Power supply is the foundation for stable operation of the development board. Understanding the power paths enables quick troubleshooting of common issues such as failure to boot on power-up, abnormal charging, and insufficient power for external peripherals, and prevents hardware damage caused by incorrect power configuration.
Application Scenarios
- Development & Debugging: Powered directly from PC via USB, supplying power to both the on-board debugger and target MCU simultaneously.
- Standalone Operation: Powered by a 3.7 V Li-Po battery to build a portable IoT node without a USB cable connection.
(Images sourced from Microchip)
Power Architecture & Power Paths
Dual Power Input Options
-
USB Power Supply
VUSB → MCP73871 Battery Charger → MIC33050 LDO Regulator → VCC_P3V3
Stable 3.3 V output feeds the on-board debugger, peripherals (ATWINC1510, mikroBUS interface) and PIC24 main MCU.
-
Battery Power Supply
VBAT (3.7 V Li-Po battery connected to the JST connector) directly supplies power to the entire system. Automatic battery charging initiates once a USB cable is plugged in.
Current Limit
The total USB input current is capped at 500 mA, shared between battery charging and target circuit operation, to avoid overloading the PC USB port.
2. Charge Management (MCP73871)
Key Electrical Specifications
- Charging Voltage: Fixed at 4.2 V; only compatible with 3.7 V nominal Li-Po batteries with a 4.2 V full-charge cut-off voltage.
- Charging Current: Factory default limited to 100 mA, suitable for small-capacity batteries (400 mAh or higher recommended to prevent overcharging).
- Timeout Protection: Maximum charging cycle duration set to 6 hours; a fault condition triggers automatically upon timeout.
LED Status Indication Table
| LED Status | Definition |
|---|---|
| Solid Red | Charging in progress |
| Solid Green | Charging completed |
| Blinking Red | Battery undervoltage (Voltage < 3.1 V) |
| Both Red & Green Lit Simultaneously | Charging timeout fault |
Related Documents
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- PIC-IoT WA Development Board ( EV54Y39A)
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