Power - Microchip Technology AVR-IoT Wx Hardware User's Manual

4.3

Power

4.3.1 Power Source
The board can be powered through the USB port or by a Li-Ion/LiPo battery. The board contains one buck converter
for generating 3.3V for the debugger, target, and peripherals.
The maximum available current from the USB is limited to 500 mA. The current will be shared between charging the
battery (if connected) and the target application section.
Figure 4-3. Power Supply Block Diagram
USB
Power Source
Battery Charger
Power Converter
Power Consumer
Cut Strap
4.3.2 Battery Charger
AVR-IoT Wx features an MCP73871 Li-Ion/LiPo charger and JST battery connector on board. The charger is
configured to limit the charge current to 100 mA to prevent the overcharging of small capacity batteries. Minimum
recommended battery capacity is 400 mAh.
The MCP73871 has a battery charge voltage of 4.2V. Make sure your battery has the same charge
WARNING
voltage.
Table 4-4. Charger Status LEDs
LEDs
Red (charging)
Red (discharging)
Green
Red and Green
4.3.3 Hardware Modifications
On the bottom side of the AVR-IoT Wx board there are two cut-straps, as shown in the figure below. These are
intended for current measurement purposes. Do not leave these unconnected as the microcontrollers might get
powered through the I/O's.
©
2020 Microchip Technology Inc.
AVR-IoT Wx Hardware User Guide
VUSB VMUX
MCP73871
Li-Ion / Li-Po
Battery
Charger
V
BAT
Function
The battery is being charged by the USB
The battery voltage is low. Triggers if the voltage is under 3.1V.
Charge complete
Timer Fault. The six-hour charge cycle has timed out before the complete
charge.
VCC_P3V3
MIC33050
cut-strap
(buck)
cut-strap
Battery
Connector
(JST)
User Guide
Hardware User Guide
nEDBG
Peripherals
mBUS
WINC1510
ATmega4808
DS50002805B-page 15