Re: USB 5volt power

On 15 Aug 2006 23:57:58 +0200, ArameFarpado
<a-farpado.spam@xxxxxxxxxx> wrote:

John wrote:
Hi, thanks for you reply

There are 2 per-port limits on the power available from a USB port.
One limit for devices that don't tell the USB controller how much
power they need and another limit for devices that do specify their
loading. If a device draws more than the first limit and does not
tell the controller, you may encounter problems. If a device
specifies it's current requirements but exceeds that specification,
you may encounter problems.

There is also a maximum total current limit for the particular USB
controller being used. If that total current limit is exceeded, the
chip will (usually) shut down. This sounds like the problem you are
describing. There are two solutions - connect fewer devices at one
time (example: printer and scanner not usually in use simultaneously)
or add an external powered hub.

John
This problem appens with a usb-adsl modem, the modem have been replaced 2
times (3rd modem allready) and did not solve the problem, the adsl
connection is a high-speed and the power goes down when the modem starts to
work harder like when doing a download... it appens with just the modem
connected.

So, do you think that connecting the modem with a diferent 5volt supply and
desconnecting the 5volt supplied by the controller is a bad idea ?

Thanks
ArameFarpado

Unless you already have the external 5 volt supply, I would suggest
getting an inexpensive powered USB hub. Most of the USB 1.1 hubs are
discounted now because people want USB 2. However, the USB 1.1 speed
is more than adequate for DSL data speeds.

John

.

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