REF: BBONEBLK_SRM
BeagleBone Black System
Reference Manual
Rev A5.2
Page 98 of 108
The
VDD_3V3B
rail is supplied by the LDO on the BeagleBone Black and is the primary
power rail for expansion boards. If the power requirement for the capes exceeds the
current rating, then locally generated voltage rail can be used. It is recommended that this
rail be used to power any buffers or level translators that may be used.
VDD_5V
is the main power supply from the DC input jack. This voltage is not present
when the board is powered via USB. The amount of current supplied by this rail is
dependent upon the amount of current available. Based on the board design, this rail is
limited to 1A per pin from the main board.
The
SYS_5V
rail is the main rail for the regulators on the main board. When powered
from a DC supply or USB, this rail will be 5V. The available current from this rail
depends on the current available from the USB and DC external supplies.
8.6.2
Expansion Board External Power
A cape can have a jack or terminals to bring in whatever voltages may be needed by that
board. Care should be taken not to let this voltage feedback into any of the expansion
header pins.
It is possible to provide 5V to the main board from an expansion board. By supplying a
5V signal into the
VDD_5V
rail, the main board can be supplied. This voltage must not
exceed 5V. You should not supply any voltage into any other pin of the expansion
connectors. Based on the board design, this rail is limited to 1A per pin to the
BeagleBone Black.
8.7
Mechanical
This section provides the guidelines for the creation of expansion boards from a
mechanical standpoint. Defined is a standard board size that is the same profile as the
BeagleBone Black. It is expected that the majority of expansion boards created will be of
standard size. It is possible to create boards of other sizes and in some cases this is
required, as in the case of an LCD larger than the BeagleBone Black board.
8.7.1
Standard Cape Size
Figure 63
is the outline of the standard cape. The dimensions are in inches.
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Страница 103: ...REF BBONEBLK_SRM BeagleBone Black System Reference Manual Rev A5 2 Page 103 of 108 Figure 65 Component Side Silkscreen...
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