This is a summary of most exceptions that can occur with the power supply.
This can happen if the target section draws too much current at a given voltage and cause the thermal shutdown safety feature of the MIC5353 regulator to kick in. To avoid this, reduce the current load of the target section.
The USB input voltage (4.4-5.25V) limits the maximum output voltage, the voltage drop over the MIC5353 regulator at a given voltage setting, and current consumption. If a higher output voltage is needed, use a USB power source that can provide a higher input voltage or use an external voltage supply on the VTG pin.
An externally applied voltage to the VTG pin without setting the VOFF pin low can cause this. If the target voltage differs more than 100 mV over/under the voltage setting, the on-board debugger will detect it, and the internal voltage regulator will shut down. To fix this issue, remove the applied voltage from the VTG pin, and the on-board debugger will enable the on-board voltage regulator when the new condition is detected. Note that the PS LED will blink rapidly if the target voltage is below 100 mV of the setting but will ordinarily be lit when higher than 100 mV above the setting.
A full or partial short circuit can cause this and is a particular case of the issue mentioned above. Remove the short circuit, and the on-board debugger will re-enable the on-board target voltage regulator.
This occurs if the target voltage is set to 0.0V. To fix this, set the target voltage to a value within the specified voltage range for the target device.
This can be the issue if power jumper J100 and/or J101 is cut, and the target voltage regulator is set to a value within the specified voltage range for the target device. To fix this, solder a wire/bridge between the pads for J100/J101, or add a jumper on J101 if a pin-header is mounted.
This is most likely caused by a high-current drain on VBUS, and the protection fuse (PTC) will reduce the current or cut off completely. Reduce the current consumption on the VBUS pin to fix this issue.