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 switched off, detecting and handling any short-circuit conditions. It will also detect and handle if an
external voltage, which causes V
CC
_TARGET to move outside the voltage setting monitoring window of ±100 mV, is
suddenly applied to the VTG pin without setting the V
OFF
pin low.
Info:
The on-board debugger has a monitoring window of V
CC
_TARGET±100 mV. The on-board debugger
status LED will blink rapidly if the external voltage is under this limit. The on-board debugger status LED
will continue to shine if the external voltage is above this limit. When removing the external voltage, the
status LED will start blinking rapidly until the on-board debugger detects the new situation and turns the
target voltage regulator back on.
3.3.2
External Supply
Instead of the on-board target regulator, an external voltage can power the PIC16F18076 Curiosity Nano. When
shorting the Voltage Off (VOFF) pin to the ground (GND) pin, the on-board debugger firmware disables the target
regulator, and it is safe to apply an external voltage to the VTG pin.
It is also safe to apply an external voltage to the VTG pin when no USB cable is plugged into the DEBUG connector
on the board.
The VOFF pin can be tied low/let go at any time, which will be detected by a pin-change interrupt to the on-board
debugger, which controls the target voltage regulator accordingly.
WARNING
Applying an external voltage to the VTG pin without shorting VOFF to GND may cause permanent damage
to the board.
WARNING
Do not apply any voltage to the VOFF pin. Let the pin float to enable the power supply.
WARNING
The absolute maximum external voltage is 5.5V for the on-board level shifters, and the standard operating
condition of the PIC16F18076 is 1.8–5.5V. Applying a higher voltage may cause permanent damage to the
board.
PIC16F18076 Curiosity Nano
Curiosity Nano
©
2022 Microchip Technology Inc.
and its subsidiaries
User Guide
DS50003399A-page 16
