D E M O 9 S 0 8 S F 4
J U N E 9 , 2 0 0 9
U S E R G U I D E
8
CAUTION:
Damage to the board may result if voltages greater than +5.5V are applied
at connector J1 input.
POWER SELECT
Power may be applied to the board through the integrated BDM circuitry, or through connector
J1. Power selection is achieved using 2 selection headers: the VOUT_SEL option header and
the VX_EN option header. Optionally, power may be sourced to external circuitry through
connector J1.
VOUT_SEL
The PWR_SEL option header allows the user to select power input either from either an
external power source connected to the VIN connector or from the integrated USB-BDM.
Figure 3 below details the PWR_SEL header connections.
Figure 3: VOUT_SEL Option Header
● 3V
5V
E5VDC to target MCU (default)
3V
E3.3VDC to target MCU
● 5V
CAUTION
:
Do not configure the target board to draw more than 300mA when
powered from the integrated USB BDM. Damage to the target board or
host PC may result otherwise.
Power from the integrated BDM is drawn from the USB bus and is limited
to
300 mA
. This
current limit accounts for the total current supplied over the USB cable to the BDM circuit, the
target board, and any connected circuitry. Current drain in excess of value violates the USB
specification and will cause the USB bus to disconnect. This may cause the board to exhibit
power cycling where the board appears to turn off and back on continually. Damage to the
host PC or the target board may result.
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