"Emanuele" <emcelettronicaNOS
...@DELETEgmail.com> wrote in message
...
> working with USB Device, i discovered that, the most important
> manufactures of the motherboards, don't monitoring the USB current draw.
Yeah, that's not exactly a well-kept secret. :-) Given the intense price
competition in motherboard manufacturing, being able to drop a current
monitoring IC is something many manufacturers will vote for.
> Do You know some motherboards that control the current over the +5V USB
> supply and so can limit the current to 100mA?
I'd suggest looking at, e.g., Intel brand motherboards -- they're much more
likely to actually implement the
USB specs (even when it "doesn't really
matter that much") that the Taiwanese manufacturers. Are there any Fry's
stores where you live? They usually have about 20 motherboards sitting out on
display, and you could carefully look at each one and probably ascertain
whether or not there's any active current limiting in place.
To tell you the truth, though, you're not going to find *any* motherboard that
"hard limits" at 100mA like a bench power supply would. Most the USB current
limiters out there have pretty wide tolerances, and have nominal trip points
typically *twice* the USB spec limit (200mA and 1A). This is ostensibly to
allow for surge current at start-up.
> What do You think about it?
The flagrant abuse of the
USB spec has actually created some useful outcomes,
such as the
USB connector becoming a standard for power adapters?
---Joel
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