For some areas like medical equipment or test equipment it is required to galvanically insolate the peripheral from the PC. This little device serves this purpose.
It can be jumpered for USB powered or externally powered. The mini USB port serves as a power connector. A cellphone AC adapter can be used as long as it is isolated. In order to insolate the USB power the Traco DC/DC converter is used.
The key part is an ADuM4160 from Analog Devices. It can do low speed and full speed. Unfortunately high speed is not supported by the ADuM4160.
The mini USB power port and USB-A device port .
The cable is connected directly to the PCB.