The FB15 and FB1 in the spots in the USB circuit where one would normally place PTC resettable fuses.
The USB OTG port must be able to supply 5V @ 100 mA to devices that are plugged in.
This is probably a PTC fuse with a "hold current" of  120 mA and a max current of 1A.

The PTC fuse prevents an attached device from using more than the permitted current.

Google "ptc fuse" to find out more about them.

I'd be certain of this if FB4 and FB5 did not appear in similar spots in the Host USB circuit with the same values. The USB spec requires a Host port to supply 500 mA of current.

Regards,
Bob Feretich

On 3/6/2012 4:27 PM, Stephen Farnsworth wrote:
That is the conclusion that I came to, as well.

On Tue, Mar 6, 2012 at 3:25 PM, David Rebbe <drebbe@intrepidcs.com> wrote:
Thots,

Without looking at the datasheet for the IC, looks like its a ferrite
bead 120 ohm.

David Rebbe
Intrepid Control Systems, Inc
31601 Research Park Drive
Madison Heights, MI 48071
1-586-731-7950 ex728


On 3/6/2012 6:18 PM, Thots wrote:
> I'm seeing an intermittent issue with the OTG USB port on my custom hardware.
> Normally it works great, but from time to time the Gumstix doesn't recognize
> when I plug in the mini-B USB cable into the OTG port.  When the Gumstix
> gets in this state, it will never detect the USB cable no matter how many
> times I load and unload the g_ether module or plug and unplug the cable. (My
> gumstix won't recognize the mini-B USB cable unless the g_ether module is
> loaded.)
>
> The OTG port always appears to work on the TOBI breakout board so I assume
> the problem must be with my custom hardware.  I was looking at the TOBI
> schematic, and page 3 deals with OTG.  There is a part on the USB_OTG_VBUS
> line labeled: “BF15/120R 1A”.  Is this part a 120 Ohm resistor or something
> else?
>
> http://pubs.gumstix.com/boards/TOBI/PCB30002-R3474/PCB30002.pdf
>
> Thanks for taking the time to read this,
> Thots
>
> --
> View this message in context: http://gumstix.8.n6.nabble.com/USB-OTG-and-TOBI-schematic-tp4552816p4552816.html
> Sent from the Gumstix mailing list archive at Nabble.com.
>
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