iMX233 battery power supply tests

Once we solved all battery power supply issues on iMX233-OLinuXino-Maxi today we tested how it works with our Li-Po battery http://www.olimex.com/dev/battery-lipo1400mah.html

We got very interesting results!

The LAN9512 USB hub + Ethernet takes about 250mA when used, total consumption is around 320 mA when all peripherials are used and Ethernet is working with the 1400mA battery this means around 4 hours of continuous operation on backup battery for iMX233-OLinuXino-Maxi.

Then we disconnected the LAN9512 to see how power hungry will be iMX233-OLinuXino-Mini and whoa during the boot the consumption is around 120mA, then at linux console working with the board the power consumption drop to 75mA! this means about 18 hours work on battery! Then we put the board in suspend mode with the PWR/REC button in this mode the processor is IDLE and just the RAM is refreshing, and the power went down to 30mA.

Now I’m really puzzled does 454Mhz ARM926J processor consumes only 45mA when run at full speed?

On Linux console running “top” show CPU use 3% when you do simple shell commands. So let’s make the CPU a bit busy with:

$ cat /dev/urandom > /dev/null &

$ top

Now we see CPU is used at 100% and the power consumption rise from 75 to 120mA! Ahaaa so Linux kernel does some kind of flexible power management depend on the CPU load, so the power consumption vary. Anyway if we assume the DDR still takes about 30mA the power consumtion of just 45-90mA of 454Mhz ARM9 processor is remarkable (well let’s not forget that iMX233 was designed with portable media player in mind so working on battery was design goal for the engineers who created it, well done!).

Conclusions:

1. on battery with USB hubs ON, Ethernet ON etc. the total power consumption is about 1.35W (4.2V x 0.32A)

2. without LAN9512 USB hubs and Ethernet the total power vary from 0.3W to 0.5W depend on CPU load

3. In suspend mode OLinuXino needs just 0.1W