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tschmidt
MVM
join:2000-11-12
Milford, NH
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tschmidt to Edrick

MVM

to Edrick

Re: "Professional" Grade or High End USB Power

USB has the notion of a unit load. Early this was 100/500ma, USB 3 increased it to 150/900 ma at 5 Volts. The purpose of having two levels is the device must power up at low value and then request permission to switch to higher consumption. All upstream ports must be able to supply at least low power on a per port basis with high power being optional. This is what makes USB powered and unpowered hubs feasible and guarantees the bus will not become overloaded.

There is a special option for charging ports, that operate as power transfer only, no data transfer. They are limited to 1.5A, the upper limit of the connector.

There is a higher voltage option, kind of like Ethernet PoE, I don't know status or how well it has been received.

That is why you are not going to see 5V 2A USB per port capability. Are you sure any of the devices you have draw more then 900 ma or 1.5A? If so I'd be surprised.

/tom

Edrick
I aspire to tell the story of a lifetime
Premium Member
join:2004-09-11
San Diego, CA

Edrick

Premium Member

If no device can accept over 1.5A then how come so many chargers tout 2.1A for one port?

tschmidt
MVM
join:2000-11-12
Milford, NH
·Consolidated Com..
·Republic Wireless
·Hollis Hosting

tschmidt

MVM

said by Edrick:

If no device can accept over 1.5A then how come so many chargers tout 2.1A for one port?

I have no idea.

/tom

robbin
Mod
join:2000-09-21
Leander, TX

robbin to Edrick

Mod

to Edrick
said by Edrick:

If no device can accept over 1.5A then how come so many chargers tout 2.1A for one port?

One word -- iPad

cwnorris
join:2000-01-17
Longmont, CO

cwnorris to tschmidt

Member

to tschmidt
Click for full size
My Asus tablet charger uses USB, but you need to have a USB 3.0 cable for it to charge at the higher rate.

»www.usb.org/developers/p ··· elivery/

LazMan
Premium Member
join:2003-03-26
Beverly Hills, CA

1 recommendation

LazMan to Edrick

Premium Member

to Edrick
said by Edrick:

If no device can accept over 1.5A then how come so many chargers tout 2.1A for one port?

The -STANDARD- says no more then 1.5A - however, there are several devices (iPad probably being the most common) that are non-standard, and draw more....