If the smartphone reboots after that failure is a USB sleeping problem. On my laptop, I have exprimented both. The USB 3 problem can be managed with some software workarounds but with an USB 2.0-only hub you will be 100% safe and the USB sleeping port which in theory should not happens when the hub sucks current but - like in my case the BIOS is tuned to give away current even if the data port is sleeping - it happens. Connecting and mounting a USB stick might solve the problem.
conclusion
Use a USB 2.0-only hub with a USB 2.0-only stick connected to it.