Instead of the on-board target regulator, an external voltage can power the PIC32CM
JH-Value Line Curiosity Nano+ Touch board. 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 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 kit.
Warning: Absolute maximum external voltage is 5.5V for the
level shifters on board. Applying a higher voltage may cause permanent damage to the
kit.
Warning: Do not apply any voltage to the VOFF pin. Let the
pin float to enable the power supply.
Programming, debugging, and data streaming are still possible with an external power
supply. The USB cable will power the debugger and signal level shifters. Both
regulators, the debugger, and the level shifters are powered down when the USB cable is
removed.
Info: The on-board debugger monitors the
voltage supplied to the board. If VOFF is not pulled low and the external power supplied
differs by more than ±100 mV from the target regulator setting, the on-board debugger
will shut off the target regulator and begin blinking the status LED rapidly, indicating
an error condition. Once the input voltage returns within ±100 mV of the target
regulator setting, the on-board debugger will switch on the target regulator and stop
blinking the status LED.
Info: In addition to the power consumed
by the PIC32CM6408JH00064 microcontroller and its peripherals, approximately 100 µA will
be drawn from any external power source to power the on-board level shifters and voltage
monitor circuitry when plugging a USB cable into the DEBUG connector on the board. When
a USB cable is unplugged, some current is used to supply the level shifter’s voltage
pins, having a worst-case current consumption of approximately 5 µA. Typical values may
be as low as 100 nA.
