-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at
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| 1962 | I love to cook with wine. Sometimes I even put it in the food.
Since USB is so, um, universal it's not surprising to find a manufacturer who keeps model numbers and prices the same but has changed the chip(s) inside which may noticeably change performance, unfortunately. I.e., the popular D-Link DUB-H7
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has been around for at least 5 years now, and has gone through multiple internal design revisions.
I have one of these that I like:
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-- pretty inexpensive and it "works fine for me."
Note that very few hubs -- almost none once you're above 4 ports -- comes with a power supply beefy enough to provide a full 500mA to all ports; I've often felt that the ratio of the power supply's current output to "number of ports multiplied by 500mA" gave at least some indication of the quality of the design. (I.e., if they cut a bigger corner with the power supply, they probably made bigger cuts elsewhere...)
Manufacturers do this, of course, since it's incredibly unlikely anyone would actually have, e.g., 10 peripherals that all truly need 500mA on a
10-port hub, so they save money with a smaller power supply.
I have not nearly that much load, but that looks like a safe bet. ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
no one says a hub must be able to supply 500mA to every port, as long as you know what you are getting I don't see how that has anything to do with quality
it's a bit like saying a heavy hammer is better quality than a light hammer
There's no reason whatsoever to *not* provide 500mA to every port other than the cost of the power supply. I think there's decent correlation between how much "downsizing" the manufacturer chose to make in the power supply to how much "downsizing" they might have done elsewhere (e.g., power protection per port? or just for the entire hub? ICs where a low-speed USB devices slow down the entire hub? Or just that one device?).
I could be wrong -- surely there are exceptions to the pattern I've noticed --, but that's my experience.
I'd say it's more like buying a bus and finding out that the average passenger on some models is only 150lbs., whereas on another model it's
300lbs. In general I'd say the bus meant for the heavy guys is going to be a bit higher quality than the one meant for the the lightweights...
The more serious hubs come with supplies for 4 amps:
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Ok, technically that only maxes out 8 of the 13 ports but it's nex to impossible to have all of them loaded to the hilt. Just like many US cars are not permanent-full-throttle proof while European ones almost have to be.
Most certainly with audio stuff. The wimpy under-rated gear often won't even survive one jam session in the garage.
AFAIK its 1A per port. So that would be 4 ports. In real situations you'll never reach the limit. Unless you intend to power several power hungry devices.
--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
nico@nctdevpuntnl (punt=.)
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Yep, that's correct for regular old USB 1.x/2.0 devices.
There are some "USB charging" specs that allows more (2A or more -- the iPad was one of the first big users of this spec, as it would've taken it annoyingly long to charge at only 500mA), but I wouldn't ask any many-port hub to provide for, e.g., 2A charging on all of its ports.
"Regular old" USB 3.0 devices can request up to 900mA, I believe. I don't expect to see too much benefit from USB 3.0 any time soon, though
-- many hard drives and memory sticks still don't max out USB 2.0 high-speed; the biggest real benefactor of USB 3.0's SuperSpeed (5Gbps) might be USB-connected video cards.
My use is primarily running an external audio card, charging cameras, and phones, and extracting photos and address-books... nothing very fast; just trying to reduce cable snarl. ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
During device enumeration, a USB peripheral will tell the hub or controller how much power it needs. For most devices, this will be far less than 500mA. (Also, I recall that USB 2.0 has a max power spec of 1.1A, not 500mA - just FYI) And even then, typical USB devices will only pull max current when they are actually in use - such as a mechanical disk drive performing a write operation, not just sitting idle on the bus.
It is quite uncommon to have so many USB peripherals all in ACTIVE use at max power at the same time, even if they are all enumerated at max power. For example, I'll bet if you hooked milliamp meters to a pair of external USB hard drives, you would see the current see-saw back and forth as the drives exchanged data with each other.
Now, that said, I suppose you could connect 7 iPhones or whatever and just try to use all those ports as a multi-purpose charger of sorts. But even then, they'll still enumerate. If the hub can't accommodate it, it will either fold them back to low power mode, or refuse to enumerate them. And yes - for a few devices a power foldback degrades performance. But it's a very rare occurance in my experience. Your mileage may differ.
I am aware that some cheaper powered-USB hubs don't enforce the power limits (or so do poorly), and with these, you do run the risk of bottoming out your available current (total connected USB load). But those are crap.
Interesting. Every USB current limiter chip I've seen / used cuts out at over 1A.
--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
nico@nctdevpuntnl (punt=.)
--------------------------------------------------------------
Strange. Do you have an example? Normally it's 500mA, and only after requesting it (else it's 100mA):
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Quote "... a self-powered port supplies 500 mA of current to each downstream port"
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Quote "The total current drawn by the bus-powered device is the sum of the current to the controller, the embedded function, and the downstream ports, and it is limited to 500 mA from an upstream port".
Quote "... functions always draw less than 100 mA; high-power functions must draw less than 100 mA at power up and can draw up to 500 mA after enumeration".
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