beaglebone-black - Flipbook - Page 37
BeagleBone Black
Fig. 6.2: High Level Power Block Diagram
6.1.1 TPS65217C PMIC
The main Power Management IC (PMIC) in the system is the TPS65217C which is a single chip power management IC consisting of a linear dual-input power path, three step-down converters, and four LDOs. LDO
stands for Low Drop Out. If you want to know more about an LDO, you can go to http://en.wikipedia.org/wiki/
Low-dropout_regulator .If you want to learn more about step-down converters, you can go to
http://en.wikipedia.org/wiki/DC-to-DC_converter
The system is supplied by a USB port or DC adapter. Three high-e昀케ciency 2.25MHz step-down converters are
targeted at providing the core voltage, MPU, and memory voltage for the board.
The step-down converters enter a low power mode at light load for maximum e昀케ciency across the widest
possible range of load currents. For low-noise applications the devices can be forced into 昀椀xed frequency PWM
using the I2C interface. The step-down converters allow the use of small inductors and capacitors to achieve
a small footprint solution size.
LDO1 and LDO2 are intended to support system standby mode. In normal operation, they can support up to
100mA each. LDO3 and LDO4 can support up to 285mA each.
By default only LDO1 is always ON but any rail can be con昀椀gured to remain up in SLEEP state. In particular the
DCDC converters can remain up in a low-power PFM mode to support processor suspend mode. The TPS65217C
o昀昀ers 昀氀exible power-up and power-down sequencing and several house-keeping functions such as power-good
output, pushbutton monitor, hardware reset function and temperature sensor to protect the battery.
For more information on the TPS65217C, refer to http://www.ti.com/product/tps65217C
6.1.2 DC Input
A 5VDC supply can be used to provide power to the board. The power supply current depends on how many
and what type of add-on boards are connected to the board. For typical use, a 5VDC supply rated at 1A should
be su昀케cient. If heavier use of the expansion headers or USB host port is expected, then a higher current supply
will be required.
The connector used is a 2.1MM center positive x 5.5mm outer barrel. The 5VDC rail is connected to the
expansion header. It is possible to power the board via the expansion headers from an add-on card. The 5VDC
is also available for use by the add-on cards when the power is supplied by the 5VDC jack on the board.
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Chapter 6. Detailed Hardware Design
