MT-DB-U2
Manual
Power Configuration
Power Configuration
The MTDBU2 can be powered in a variety of ways by utilizing solder jumper J8 located on
the bottom of the board. By default, the board is configured to be powered via USB, with Vcc at 5V,
and the microcontroller internal 3.3V regulator enabled and powering only the USB pads. The
microcontroller clock is configured at boot to run at 8MHz. The following lists some of the
configurations possible. Code may have to be recompiled when switching configurations (ie: to
change cpu clock speed and/or internal regulator power).
Power Configuration
Jumper J8
Regulator Max CPU
USB bus powered – 5V Vcc (default)
3.3V Vcc = 5V = UVcc Vcc
Enable
16 MHz
USB Bus powered – 3.3V Vcc
3.3V = Vcc 5V = UVcc Vcc
Enable
8 MHz
Externally powered – 4.0 to 5.5V Vcc
3.3V Vcc 5V UVcc = Vcc
Enable
16 MHz
Externally powered – 3.0 to 3.6V Vcc
3.3V = Vcc 5V UVcc = Vcc
Disable
8 MHz
WARNING
Care must be taken when configuring the solder jumpers.
It is possible to cause permanent damage to the device or the
power supply by improperly setting the jumpers.
Do not change any jumpers while the unit is powered.
When using the microcontrollers internal regulator to power itself,
be sure not to exceed the regulator maximum current output.
USB Bus Powered 5V
By default, the MTDBU2 is configured for 5V from the USB connector (Vbus). In this
configuration, solder jumper J8 is set such that Vcc and UVcc are connected to Vbus (5V). The AVR
internal 3.3V regulator must be enabled (default setting). This will supply 3.3V to the USB pads and
3.3V header pin.
USB Bus Powered – 3.3V
The internal 3.3V regulator can be used to supply the AVR itself with 3.3V. In this configuration,
solder jumper J8 is set such that Vcc is connected to 3.3V and UVcc is connected to Vbus (5V). The
AVR internal 3.3V regulator must be enabled (default setting). This will supply 3.3V to the AVR itself,
October 29, 2015
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