General > General Technical Chat
What happens when you draw too much current from a usb port?
chrisb741:
I have test equipment to accurately test load, as long one port limits power to 100mA I'm satisfied that's the limit for these other people reporting problems. As mentioned even the basic uC dev boards use 50-75mA. Does not leave much from 100mA
Dan123456:
I had the mother board fail on my work laptop not too long ago and it took the dongle for my headset out with it.
I don’t know exactly what went wrong with it but plugging the dongle into a different laptop gave me a pop up saying “USB port drawing too much current” and that would keep popping up every 10 seconds or so.
As it was work equipment, I didn’t want to / wouldn’t be allowed to mess around with it / dig further but I would guess maybe the computer was getting the message that it was pulling to much current, killing power to the port, then retrying after a set period of time.
Ether that or the dongle had an intermittent fault :P
chrisb741:
I've had just a cable intermittently cause a popup saying the last device I plugged in has failed
mariush:
I've seen resettable fuses on motherboards ...for example a 2.4A fuse on 4 usb 2.0 ports or 2 usb 3.0 ports.
Buriedcode:
All host posts I've seen (not charging ports from plug in PSU's) have had both resetable SMD fuse and a USB power distribution switch that monitors current and allows software control of the power to that port. The current limits aren't particularly accurate, and provide a single pin state output for overcurrent. Those IC's also have thermal shutdown and short circuit protection.
These are generally "good enough" to protect the host from shorts, and will have some leeway as to the maximum current. In the past decade or so I haven't seen a host limit to 100mA but I'm only going for the PC's, lpatops and tablets I've used.
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