Does anyone have the ability to test the current output for USB host? I have been seemingly endlessly searching for the current output capabilities of the Galaxy S 3, the Galaxy Note 2, and the Nexus 7 to no avail. Reading some of the Wikipedia entry on USB, it would seem that USB 1.0 and 2.0 will allocate 100mA blocks to devices. Logically, one would assume that Android devices would be designed to output at least 100mA, and possibly greater output currents (in 100mA increments, perhaps).
I would love to know what the current capabilities are, so I can plan accordingly with connecting USB hard disks and other devices. My Nexus 7 could not fully power a 0.75A hard disk (I knew this beforehand, but tried anyway to see what would happen), and the disk started spinning but would keep spinning down.
The 500GB 7mm slim drives consume about 1.2W (according to the specsheet), so 240mA would be required on the Android device (possibly more to power the USB-SATA Adapter.) Anandtech.com's review of the Crucial M4 shows that even SSD drives consume too much power to be fully powered by Android devices. I should be able to test a Crucial M4 512GB SSD soon, although I expect it won't work properly.
Hopefully, the Galaxy Note 2 will bring some more USB host power to the table.
If anyone knows how the Galaxy S 3 and the Nexus 7 compare in USB output power, feel free to chime in!
EDIT: Okay, so I'm slightly boggled. The Crucial website shows that the active power consumption of the drive is 0.15W, and that idle is 0.065W. This would mean that the Note 2 or the Nexus 7 could likely power the Crucial M4. This is contradictory to Anandtech.com's review of the drive power consumption. 500GB of SSD storage via USB OTG with the Wolfson DAC on the Galaxy Note 2 would be.... awesome.
Edited by headfinoob - 11/22/12 at 7:33am