
REF: BB_SRM_xM BeagleBoard-xM System
Reference Manual
Revision A2
Page 50 of 164
R9
620K,1%,0603
R12
330
GRN
D5
LTST-C190GKT
AUX_3V3
R10
200K,1%,0603
PWRLED_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
GND
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
8.4 Meter Current Measurement
Jumper J2 is a header that allows for the voltage drop across the resistor to be measured
using a meter, providing a way to measure the current consumption of the BeagleBoard
from the main voltage rails, either USB or DC. The resistor, R13, is a .1 ohm resistor
across which the voltage is measured. The reading you get is .1mV per mA of current.
You will need to make sure you have a sensitive meter to make your measurements.
Please keep in mind, that this current reading does not include any current consumed by
the USB HUB, USB ports, or the Expansion headers.
8.5 Processor Current Measurement
The resistor across J2 can also be used to measure the current of the board by reading the
voltage drop across R13 from software. There are two pairs of resistors provided on the
TPS65950 that measure the voltage on either side of R13. This is done via the I2C
control bus to the TPS65950 from the processor. These values along with resistance of
R13 are used to calculate the current consumption of the board. Figure 24 is the
schematic of the measurement circuitry. The maximum value that can be input to the
ADC inputs is based on the setting of the VINTANA2.OUT voltage rail which defaults
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