REF: BBONEBLK_SRM
BeagleBone Black System
Reference Manual
Rev A5.2
Page 39 of 108
6.1.3
USB Power
The board can also be powered from the USB port. A typical USB port is limited to
500mA max. When powering from the USB port, the VDD_5V rail is not provided to
the expansion header. So capes that require the 5V rail to supply the cape direct,
bypassing the
TPS65217C
, will not have that rail available for use. The 5VDC supply
from the USB port is provided on the SYS_5V, the one that comes from the
TPS65217C
,
rail of the expansion header for use by a cape.
Figure 24
is the connection of the USB
power input on the PMIC.
DGND
C1
10uF,10V
U2
TPS65217C
USB
12
C36
0.1uf ,6.3V
DGND
P4
mini USB-B
D-
2
D+
3
VB
1
ID
4
G2
7
G3
6
G1
5
G5
8
G4
9
DGND
Figure 24.
USB Power Connections
6.1.4
Power Selection
The selection of either the 5VDC or the USB as the power source is handled internally to
the
TPS65217C
and automatically switches to 5VDC power if both are connected. SW
can change the power configuration via the I2C interface from the processor. In addition,
the SW can read the
TPS65217C
and determine if the board is running on the 5VDC
input or the USB input. This can be beneficial to know the capability of the board to
supply current for things like operating frequency and expansion cards.
It is possible to power the board from the USB input and then connect the DC power
supply. The board will switch over automatically to the DC input.
