Digilent Wi-FIRE Reference Manual page 8

An external 5V regulator can be used. This would be desirable, for example, when operating from
batteries. An external switching mode 5V regulator could be used to provide higher power efficiency
than the on-board linear regulator. In this case, use wires as appropriate to connect VU to the
unregulated input of the external regulator. Connect the regulated 5V output to 5V0. Connect GND
to the ground connection of the external regulator. Optionally, connect EN Ext to the enable input
control of the external regulator, if available. This allows the external regulator to be turned off for
low power operation. Digital pin 50 is then used to turn on/off the external regulator.
The PIC32MZ microcontroller is rated to use a maximum of 60mA of current when operating at 200
MHhz. The MRF24WG0MA WiFi module typically consumes a maximum of 237mA when
transmitting. This allows approximately 303mA of current to power the remaining 3.3V circuitry on
the WiFire board and external circuitry powered from the VCC3V3 bus. No circuitry on the WiFire
board is powered from the VCC5V0 power bus, leaving all current available from the 5V regulator to
power external circuitry and the USB 5.0Vv power bus when the WiFire is used as a USB Host.
The POWER connector (J5) is used to power shields connected to the WiFire board. Pin 1 is
unconnected, the following pins are provided on this connector:

IOREF (pin 2): This pin is tied to the VCC3V3 bus.

RST (pin 3): This connects to the MCLR pin on the PIC32 microcontroller and can be used to
reset the PIC32.

3V3 (pin 4): This routes the 3.3V power bus to shields.

5V0 (pin 5): This routes 3.3V or 5.0V power to shields depending on the position of JP9.

GND (pin 6, 7): This provides a common ground connection between the WiFire and the
shields. This common ground is also accessible on connectors J2 and J3.

VIN (pin 8): This connects to the voltage provided at the external power supply connectors
(J14 and J15). This can be used to provide unregulated input power to the shield. It can also
be used to power the WiFire board from the shield instead of from the external power
connector. If no power is supplied at J14 or J15 or from the shield, VIN will not have any
power on it.