Limiting current on a USB2-HUB4BC


#1

I’m using a USB2-HUB4BC with a device that is sensitive to large current draw (due to other devices connected to the USB host). Apparently, this hub will continue to pull up to 500mA from the host even when connected to the external power supply. This is within the spec, so it’s not a design issue, just a problem for my setup. I’d like to make a modified USB cable with a resistor on 5v wire to limit the current, and I was curious if there’s an internal resistor limiting the current to 500mA that I’ll be putting this in series with, or if that’s handled directly by the IC in the hub. In either case, would I risk damaging the hub with this sort of modification to the USB cable? I’m planning on using a 100 ohm (1/4 watt) resistor to limit the current to 50mA, and the hub will be connected to external power at all times.


#2

Hi Blane,

Thanks for asking!

I think the best thing if you are going to modify a cable (and please note that we cannot officially support or endorse such an action) would be to just disconnect the 5V VBUS between the hub and computer (clipping the red wire in the USB cable). If you use a resistor you could introduce some voltage drop and that could cause unexpected behavior from the hub.

Good luck!


#3