Just wondering what you guys thought.
I think a lot of cheap USB hubs will "backpower" the uplink port along with the downstream ports. This is technically dangerous if the PSU is not current limited. A lot of cheap hubs aren't.
Then there are the hubs that have a diode that prevents back feeding. Well, this means when using host power, you just lost 0.3 to 0.7 volts times current draw of power (I would hope they would put a Schottky there at least). This is also not very pleasant.
Anyone seen hubs that have a MOSFET there to power downstream ports when the hub isn't used in powered mode? Perhaps all the "high quality" hubs are done this way?
I've only seen cheap crappy hubs so far, just wondering what people have been seeing. And yes it's related to the OTG issue I alluded to in another thread, I suspect somehow it's "good" to backpower the host port so it could charge the host as well as supply power to downstream devices? Or not, because OTG hosts could also be supplying power? Or by definition they should never supply power so you must use a powered hub?
So many different variations...
I think a lot of cheap USB hubs will "backpower" the uplink port along with the downstream ports. This is technically dangerous if the PSU is not current limited. A lot of cheap hubs aren't.
Then there are the hubs that have a diode that prevents back feeding. Well, this means when using host power, you just lost 0.3 to 0.7 volts times current draw of power (I would hope they would put a Schottky there at least). This is also not very pleasant.
Anyone seen hubs that have a MOSFET there to power downstream ports when the hub isn't used in powered mode? Perhaps all the "high quality" hubs are done this way?
I've only seen cheap crappy hubs so far, just wondering what people have been seeing. And yes it's related to the OTG issue I alluded to in another thread, I suspect somehow it's "good" to backpower the host port so it could charge the host as well as supply power to downstream devices? Or not, because OTG hosts could also be supplying power? Or by definition they should never supply power so you must use a powered hub?
So many different variations...
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