Defective USB devices can destroy the USB port or even the motherboard of your PC. Special devices, such as a USB killer, actually serve this purpose. Furthermore, measuring devices with a USB connection can deliver incorrect measurement results due to ground loops, or even cause short circuits. This 2.5kV USB 2.0 Isolator with 200mA power supply and full speed (12Mbps) support is a sim...
I used this circuit to complete my KhudaydusUno 32 bit MicroController board
thus I could protect any accedent shorting between +3.3V & +5V ports. Thus preventing any damage may occurs on PIC32 Chip (supplied with+3.3V)