Info:
The power MUX allows the board to be powered by either USB port. If both USB power sources are
connected, the MUX will select the target USB port to power the board.
3.3.1
Target Regulator
The target voltage regulator is a MIC5353 variable output LDO. The on-board debugger can adjust the voltage output
supplied to the board target section by manipulating the MIC5353’s feedback voltage. The hardware implementation
is limited to an approximate voltage range from 1.7V to 5.1V. Additional output voltage limits are configured in the
debugger firmware to ensure that the output voltage never exceeds the hardware limits of the PIC24FJ64GU205
microcontroller. The voltage limits configured in the on-board debugger on PIC24FJ64GU205 Curiosity Nano are
2.0-3.6V.
Info:
The target voltage is set to 3.3V when the board is manufactured. It can be changed through the
MPLAB
®
X IDE project properties. Any change to the target voltage is persistent, even after a power
toggle. The resolution is less than 5 mV but may be limited to 10 mV by the adjustment program.
Info:
The voltage settings setup in MPLAB
®
X IDE are not immediately applied to the board. The new
voltage setting is applied to the board when the debugger is accessed in any way, like pushing the Refresh
Debug Tool Status button in the project dashboard tab or programming/reading program memory.
Info:
There is a simple option to adjust the target voltage with a drag-and-drop command text file to
the board, which supports a set of common target voltages. See section
for
further details.
The MIC5353 supports a maximum current load of 500 mA. It is an LDO regulator in a small package, placed on a
small printed circuit board (PCB), and the thermal shutdown condition can be reached at lower loads than 500 mA.
The maximum current load depends on the input voltage, the selected output voltage, and the ambient temperature.
The figure below shows the safe operating area for the regulator, with an input voltage of 5.1V and an ambient
temperature of 23
°
C.
Figure 3-5. Target Regulator Safe Operation Area
The voltage output of the target regulator is continuously monitored (measured) by the on-board debugger. If it is
more than 100 mV over/under the set device voltage, an error condition will be flagged, and the target voltage
regulator will be turned off. This will detect and handle any short-circuit conditions. It will also detect and handle if an
Curiosity Nano
©
2021 Microchip Technology Inc.
User Guide
50003124A-page 15