USB 2.0  4-PORT HUB -  FE 1.1 S  IC

I bought this 4 port hub to expand the USB ports of my Raspberry Pi model B. When I tried to connect two flash drives at the same time it stopped working. It is a cheap one so I was not expecting great performance from it but I hoped that it would work. All things considered it was worthwile to try a couple of things to make it work as it should be. I looked for the datasheet here. 

I compared the info on the datsheet and how it had been implemented in the circuit that I had in front of me. I found a discrepancy/difference on a capacitor (pin20)  with a much lower value, I replaced the 10uF16V  (very cheap one) with a 100uF 10V low ESR electrolytic. While looking for the datasheet, I found a recommendations page which suggests a ceramic type. (hard to find)

I tried now and works better but fails when I connect the fourth device. This seemed to me that there was a power problem. So I tried a 47uF/100uF 16V electrolytic cap as close to each Vdd upstream connection next to each connector, with a ceramic multilayer 0,1 uF 50V NPO cap for decoupling and noise filter. Tried again and now it became far more stable. Still, every now and then and in particular when the fourth device is connected, it resets itself but it is a huge improvement compaired to how it worked at the beggining. Cheap stuff, hard to make it work, poor results.

Electrolytics (I used what I had) + ceramics....

News !! I kept working in improving the stability and eventually I find out that cutting the length of the cable to about 15cm, made the hub STABLE and works correctly without re-setting the ports !!!

Job done !!