Maker Pro
Maker Pro

Motherboard and USB Compliance

E

Emanuele

Jan 1, 1970
0
Hello,

working with USB Device, i discovered that, the most important
manufactures of the motherboards, don't monitoring the USB current draw.

The +5V of the USB is directly connected to the +5V of the Power Supply
(there is only a fuse/polyswitch)
So, all motherboards aren't compliance to the chapter 7 of the USB
Specifications!

Do You know some motherboards that control the current over the +5V USB
supply and so can limit the current to 100mA?
(in the enumeration process or in a possible overcurrent situations)
What do You think about it?

Emanuele

--
*** YOUR ELECTRONICS OPEN SOURCE ***

http://dev.emcelettronica.com
;---------------------------------------------------------
(Full Projects and resources)
 
J

Joel Kolstad

Jan 1, 1970
0
Emanuele said:
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
 
E

Emanuele

Jan 1, 1970
0
To tell You the truth,
i saw the Intel's Motherboards, at the first,
and they haven't the current limit IC.
In my city (Rome) there are many hardware's store
and i'll like to spy the MB..... perhaps next weekend.

Do You know some MBs that have the current limit IC?
Can You post a picture?

Emanuele

P.S.
The flagrant abuse of the USB spec has actually created some useful
outcomes, such as the USB connector becoming a standard for power
adapters?

This is not the right way to go in heaven !!
(electronic's heaven)

--
*** YOUR ELECTRONICS OPEN SOURCE ***

http://dev.emcelettronica.com

;---------------------------------------------------------
(Full Projects and resources)
 
Top