USB standard gone INSANE?

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#1
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I've read an interesting article about the USB.
The standard specifies that the plug HAS to give 500mA, but it does NOT specify how much it CAN give. They've wrote it's in some cases 5A!!! Are they insane or is it me?

pS. it waz in Maxim something newsletter... :?:

There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

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They aren't insane.

Nothing wrong with offering more current than necessary. The load will only take what current it needs.

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I think that only for very short periods of time, if it is not any mistake in the standard. the mosfet regulator (if this is the case) may have max current 5A but don't count on it!
I think that you may count only on 500mA. but i didn't read maxim's newsletter.
And anyway, who need 5A from USB. Maybe some hard drives?

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daqq,

Can you give us a link to the Maxim article.

And the USB is not insane. It was designed by a committee. Actually I'm not sure one can differentiate the difference.

Smiley

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daqq wrote:
I've read an interesting article about the USB.
The standard specifies that the plug HAS to give 500mA, but it does NOT specify how much it CAN give. They've wrote it's in some cases 5A!!! Are they insane or is it me?

pS. it waz in Maxim something newsletter... :?:

Normal USB 1.1 and 2.0 allowes max 500mA per port.
Each port is guarantied to source 100mA. If a device needs more it has to *ask* for it and the controller may deny the request!

What the newsletter was probably talking about is a extention to the current USB standard for industrieal env. where a port may source up to 5A.

Bertolt