Re: High Power USB hub port...

SMS <scharf.steven@xxxxxxxxxxx> writes:

However if you look at how the USB power circuit is designed on
notebooks, you'll see why this is rarely necessary. Four USB ports will
share a single power controller. The power controller will limit total
current through the four USB ports to 2.0A (500mA per port). However
each individual port won't cut off with over-current protection at
501mA, in reality they'll cut off somewhere closer to 1.0A. Of course
you can't use all four of them at 1.0A because the total current is
limited to 2.0A. Since most USB devices are low-current devices or are
devices that are not powered by the bus, you're usually just fine with a
single power plug on the higher current drives.

However, this probably won't work with desktop USB ports. The USB2
PCI cards I've looked at have one "fuse" per port. That's probably
cheaper than a power controller, since regulated +5V is already
available from the bus connector. But it means if you want to draw more
current than the fuse rating, you'll need to use 2 ports. (They aren't
really fuses; they are self-resetting polyfuse things).

I'd expect motherboard USB ports to be similar, but I haven't looked.

Dave

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