Re: USB 802.11 adaptor

["Jared D. McNeill" <jmcneill%invisible.ca@localhost>]

These fuses were removed in rev. 2 RPI IIRC.

On 2013-03-19, at 5:54 PM, Jochen Kunz <jkunz%unixag-kl.fh-kl.de@localhost> 
wrote:

> On Tue, 19 Mar 2013 12:30:49 -0700
> Andy Ruhl <acruhl%gmail.com@localhost> wrote:
> 
>>> The problem isn't total power consumtion, but short peaks that exceed
>>> the max. 0.5 A for USB. This happens e.g. on sending a packet.
>> Power supplies can often handle short spikes without a lot of impact.
>> Depending on their design of course.
> Often you can find electronic fuses on USB ports. They sense current
> and switch power off of the asscociated USB port when the max. current
> is exceeded. They are quite fast in doing this, so spikes from a WLAN
> device may trigger them. (I am not talking about "poly fuses".) These
> things are smal chips, e.g. in a SO8 package, and switch power by the
> means of a MOSFET. Usually this MOSFET is controlable by the host CPU
> to switch power on and some can trigger an interrupt if the current
> limit is reached. E.g. the Olinuxino Mini uses a SY6280 for this.
> -- 
> 
> 
> \end{Jochen}
> 
> \ref{http://www.unixag-kl.fh-kl.de/~jkunz/}
>