The VCC Header contains 5.0 Volt VCC and GND that must be used to power the target device placed in the prototype area of the Atmel AVR Dragon board. The voltage can also be used to power an external target board, but it is important that the current consumption is less than 300mA. Note that the AVR Dragon current sourcing capabilities are also limited by the amount of current the Host USB controller can deliver.
Note:
If the current consumption excedes 300mA, then this may lead to errors or disconnects during programming or debugging. If the AVR Dragon starts misbehaving try to remove the load by applying external power to your circuitry and removing the VCC header connections.