6.1.7 Power Consumption
The power consumption of the board varies based on power scenarios and the board boot
processes. Measurements were taken with the board in the following configuration:
DC powered and USB powered
HDMI monitor connected
USB HUB
4GB Thumbdrive
Ethernet connected @ 100M
Serial debug cable connected
Table 4 is an analysis of the power consumption of the board in these various scenarios.
Table 4. BeagleBone Black Power Consumption(mA@5V)
MODE USB DC DC+USB
Reset TBD TBD TBD
Idling @ UBoot 210 210 210
Kernel Booting (Peak) 460 460 460
Kernel Idling 350 350 350
Kernel Idling Display Blank 280 280 280
Loading a Webpage 430 430 430
The current will fluctuate as various activates occur, such as the LEDs on and
uSD/eMMC accesses.
You can put the boar din a sleep mode depending on how much asleep you want too go. You can turn of the 3.3V rail and the 1.8V rail to save power by writing I2C commands to the TPS65217C… I don’t know what peripherals you still want to be active so this may not work…
You can power down the HDMI by sending I2C commands to it, but it may or may not save you the amount of power you are looking for.
I have three questions about BBB power consumption:
(1) Does anyone have a measurement of BBB power consumption when CPU sleeps and all peripherals are off through software command?
(2) Does anyone know whether its PRU can still run while CPU sleeps? We intend to use PRU to read data from a SPI bus, timestamp it and write to flash. Is it possible to be done without CPU involvement?
(3) What is the lowest CPU speed of BBB through voltage scaling and what will be its power consumption difference comparing to highest speed? We also intend to change the CPU speed to reduce power consumption, as out task is not so computing intensive all the time.
(4) Looks like the default OS of BBB (e.g., Angstrom) does not support sleep mode, anyone knows a way to patch it? Becaue of that we currently plan to use either TI’s linux or android for this purpose. Any suggestions?
I think a variation on this question is: Can I run a BBB using just a 3.3V supply? At first glance, there’s not a lot using 5V [Other than USB].
I note the 1.5V supplies etc. are from the TPS65217C - and it’s main input is that 5V.
If I used an external 3.3V supply, applied to the expansion header [or the battery access pads] would that be enough to power up?
Which components would be most affected by losing the 5V?
It is worse than that. The tps65217 recommended 3.7V LI+ single cell battery will not adequately power the system, either. The LDOs in the tps65217 have 200mV drop-out, so they will work with a fresh battery (but start to droop as the battery gets below 3.5V). The real problem is the TL5209 – which has a 500mV drop-out.
If somebody really wants to use the LI+ battery, one possibility would be to forget the warrentee and kludge in a tps77533d in place of the TL5209. Those PLM guys at TI have it spec’d at 0.169V dropout at 500mA. Three significant figures! Geese…
HDMI cannot be powered down without taking down the 1.8V rail. You can certainly take down all the rails via the PMIC, but that may be too low in power as that would shut everything down.
If HDMI is not connected, no cable, the framer does go into a lower power mode. You could also take the LCD pins and turn them off, either high or low, to save some power as well.
To turn ff rails, send I2C commands to the PMIC. refer to the datasheet…But, be careful not to have devices partially powered, devcies off and signal pins still active.
Excuse my beginner question. How exactly would I do that or where could I learn how to do that?
I never sent any I2C command to anybody and have no clue how to
Well, that requires software and needs to be built into the power management layer. 3.8 kernel does not have a lot of power management, but some of the newer kernels do, like 3.12. You can also do voltage and frequency scaling to lower the power, but that will also require some SW expertise…
