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REF: BB_SRM_xM
BeagleBoard-xM System
Reference Manual
Revision C2
Page 52 of 163
DC power connected and there is no USB OTG port connected. For this reason, is
recommended however, that a large pullup be provided on the daughtercard to make the
signal a logic level “1” (5V) to detect the true state of the DC jack. It is always possible
that at any point a USBOTG cable could be installed. This means that in order to power
the board from the expansion headers, the DC dummy jack must be installed and there is
a method to verify that condition.
7.3.4
AUX 3.3V Supply
The
TPS2141
has an integrated 3.3V LDO which is being used to supply the
3.3V
as
required on the BeagleBoard for the
DVI-D
interface and the
UART
. The input to the
LDO is supplied by the main
DC_5V
. This insures that the power to the LDO can be
supplied by either the USB or the DC wall supply and that the current measurement
includes the 3.3V supply. The 3.3V supply can be turned off by activating GPIO1 on the
T
PS65950
to a 1. By default the voltage is on. You will also see that the 3.3V supply
powers the power LED,
D5.
If during a low power mode, the user chooses to turn of the
power LED, this GPIO pin can be used to turn off the power LED. It should also be
noted, that the 3.3V rail controls the serial port power, so this will be powered down as
well.
Figure 22
is the AUX 3.3V Supply design.
R9
620K,1%,0603
R12
330
GRN
D5
LTST-C190GKT
AUX_3V3
R10
200K,1%,0603
PW
R
LE
D
_R
U18A
SN74LVC2G06DCKR
1
2
5
6
C204
0.1uF,10V
VIO_1V8
POWER
3V3_ADJ
U2
TPS2141PWP
LDO_IN
4
LDO_EN
6
SW_IN
2
G
N
D
7
LDO_PLDN
10
LDO_OUT
11
ADJ
9
LDO_PG
8
SW_OUT
12
SW_PLDN
14
SW_PG
1
SW_EN
5
SW_IN
3
SW_OUT
13
PPAD
15
VBAT
C207
4.7uF,6.3V,0603
R8
10K
R54
10K
U7A
TPS65950
GPIO.1/CD2/JTAG.TMS
N12
Figure 22.
AUX 3.3 Power Section
Содержание XM C2
Страница 33: ...REF BB_SRM_xM BeagleBoard xM System Reference Manual Revision C2 Page 33 of 163 Figure 5 USB OTG Connection ...
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