D E M O 9 S 1 2 X D T 5 1 2
J U L Y 1 8 , 2 0 0 8
10
POWER
The DEMO9S12XDT512 is designed to be powered through the USB-Multilink BDM during
application development. A 2.0mm barrel connector has been applied to support stand-alone
operation and to support LIN functionality. The board may also be powered through connector
J1. This connection may also be used to supply power from the board to external circuitry.
During application development, the board should be configured to draw power from the USB-
Multilink BDM. The barrel connector may be used to support LIN functionality during applica-
tion development. The barrel connector input is also used to provide power during stand-alone
operation.
POWER SELECT
Power may be applied to the board through the integrated USB-Multilink BDM circuitry, a
2.0mm barrel connector, or through connector J1. Power selection is achieved using 2 selec-
tion headers: PWR_SEL option header and the VX_EN option header.
PWR_SEL
The PWR_SEL option header selects power input either from the integrated USB-Multilink
BDM circuitry or from the on-board voltage regulator. The figure below details the PWR_SEL
header connections.
Figure 3: PWR_SEL Option Header
VB
PW
1
2
3
PWR_SEL
CONFIGURATION
1 – 2: Selects power input from
USB-ML12
2 – 3: Selects power input from on-board regulator or J1
NOTE:
Set PWR_SEL jumper to VB during application development. Use barrel connector in-
put (PWR) to support LIN functionality as needed.
Power from the integrated BDM is drawn from the USB bus and is limited
to
500 mA
. This cur-
rent limit describes the total current supplied over the USB cable to the BDM, target board and
any connected circuitry. Current drain in excess of 500 mA will violate the USB specification
and may result in damage to the host PC or the target board. At minimum, excessive current
drain will cause the host PC to spontaneously reboot. Power is provided through the inte-
grated BDM to the target board.
The on-board voltage regulator (VR1) accepts power input through a 2.0mm barrel connector
(PWR). Input voltage may range from +6V to +18V. The voltage regulator (VR1) provides a
+5V fixed output limited to 250mA. Over-temperature and over-current limit built into the volt-
age regulator provides protection from excessive stress. Consider the maximum output cur-
rent limit of VR1 when attempting to power off-board circuitry through connector J1.
