7-port USB hub with improved power output
This USB-hub is a result of a development project I did for Ericsson. For that, I needed a multi-port USB-connection to hook up several audio codecs to a single PC.
The best way to solve that was to build a plain USB 2.0 compatible hub. For that, I needed a chip solution that could handle 7 port in a easy way. After some research,
I ended up with a chip from SMSC. Before starting off with the real project, I needed to test the USB-chip by itself to learn how it works. By other means, I needed a
development board. And that is what you see here.
To make the development board more useful even when its primary purpose was over, I added a feature to it that wasn't needed by the original project: improved power
output at the +5V for USB devices. This was done by adding switching regulators for each USB-port. Four ports are able to deliver up to 1 A per port and three 500 mA.
By doing this, I went a little bit outside the USB specification regarding power handling. First of all, the USB host (the computer mostly) aren't aware about this
power design. It will not detect any power problems caused by faulty USB-devices. The good side of this is that all power is always available for the devices. The risk
of overloading or shorting the outputs are taken care internally of the regulators, so there no cause for worries anyway. I had no problems with running an old 5 GB 2.5"
laptop drive directly from the hub.
If you like to make one yourself - feel free to do it. The schematics and PCB layout are all there. The board is standard size (160 x 100 mm) and it is double sided.
Most parts are hole mounted except for the SMSC-chip and some regulator components. Note that there is an error in the PCB. A 1.0 Mohm resistor (R22) is missing and
must be mounted in parallel with the crystal afterwards (do it at the rear side). Otherwise, the hub will not work.