Figure 4-6. VBUS Output Voltage vs. Current
4.3.4
Power Supply Exceptions
This is a summary of most exceptions that can occur with the power supply.
Target Voltage Shuts Down
This can happen if the target section draws too much current at a given voltage. This will cause the thermal shutdown
safety feature of the MIC5353 regulator to kick in. To avoid this, reduce the current load of the target section.
Target Voltage Setting is Not Reached
The maximum output voltage is limited by the USB input voltage (specified to be 4.4-5.25V), and 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.
Target Voltage is Different From Setting
This can be caused by an externally applied voltage to the VTG pin, without setting the VOFF pin low. If the target
voltage differs more than 100 mV over/under the voltage setting, it will be detected by the on-board debugger, and
the internal voltage regulator will be 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 be blinking rapidly if the target voltage is below 100 mV of the setting, but will be lit normally when it is
higher than 100 mV above the setting.
No, Or Very Low Target Voltage, and PS LED is Blinking Rapidly
This can be caused by a full or partial short-circuit and is a special case of the issue mentioned above. Remove the
short-circuit, and the on-board debugger will re-enable the on-board target voltage regulator.
AVR128DB48 Curiosity Nano
Curiosity Nano
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2020 Microchip Technology Inc.
User Guide
DS50003037A-page 18
