The VTG voltage is the supply voltage to the target AVR microcontroller. It is connected to the AVR's VCC pin. VTG can either be generated by
STK600, or it can be supplied from an external source.
On-board VTG source
The on-board VTG source is set from AVR Studio. To use this source, the VTARGET jumper must be mounted. The on-board supply can be
adjusted from 0.9 to 5.5V in steps of 0.1V.
VTG can also be set to 0V, but due to hardware limitations, onboard generated VTG can not be set between 0 and 0.9V.
Note: Always check the AVR datasheet for operating voltage range before adjusting VTG.
Powering STK600 from USB
When STK600 is powered through the USB cable approximately 300 mA can be delivered to the target section.
Powering STK600 from an external DC source
If an external DC jack input is used approximately 1A can be delivered to the target section.
External VTG
If the VTARGET jumper is removed, VTG must be supplied from an external source. Connect the external source to one of the VTG pins on any of
the PORT headers. Always connect common ground (GND) when using an external VTG voltage.
When using an external source, the user must ensure that VTG is larger than any of the AREF voltages.
Note: The kit must always be powered when using an external VTARGET supply. If VTG voltage is supplied from an external source while the
main power switch is in the off position the kit may become damaged.
Status LEDs
VTARGET LED
A green LED next to the VTARGET jumper will be lit when there is a voltage of 0.9V or higher available on the VTG net.
STK600 Status LED
If a short circuit is detected when using the on-board VTG supply, the STK600 status LED will blink red.
Analog Reference Voltages
The AVR's A/D converter needs a reference voltage to set its converting range. STK600 can supply two of these voltages, AREF0 and AREF1.
For all tinyAVR and megaAVR devices, only the AREF0 is connected trough the routing card, whilst for xmegaAVR devices, AREF0 is connected
to the positive reference input and AREF1 is connected to the negative reference input on reference 0.
If the AREF0/AREF1 jumpers are mounted, the on-board Analog Reference Voltage sources are connected to the
target AVR’s AREF pins. The On-board Analog Reference Voltages can be adjusted from the PC software in the
range 0 to 5.5V, but not above VTARGET. The resolution and accuracy is 10mV.
The AREF0 and AREF1 generated voltages can also be connected to the analog comparator.
The target AVR’s AREF signals are accessible on the AUX header. The figure below shows the connection of the
AREF signals, the target section and the AREF sources.
Page 11 of 35
STK600 User Guide
2008-06-20
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