Isolated USB Isolating USB reduces noise and eliminates ground loops. But unlike optocouplers, IsoLoop isolators have unlimited life with no degradation. Illustrative circuits are shown below: Isolated USB UART Using an IL712
Isolating the input to a USB controller (rather than the bus lines) requires fewer isolation channels, and is therefore usually the simplest solution as shown in the following illustrative circuit:  The Microchip MCP2200 is a USB 2.0 to UART Protocol Converter. The IL712/IL721 Series are best-in-class bidirectional isolators with a remarkable 100 ps of jitter, and parts are available in unique MSOPs to reduce board space.  IL712-Series
product details IL712-Series data sheet
Isolated USB Controller Using IL710s
The IL710’s output enable makes it ideal for bidirectional interfaces such as USB. In this illustrative circuit, the directional output (pin 27) of the PLX/NetChip NET2890 transceiver enables the isolator channels in the active direction:  The IL710 is available in a unique MSOP for five channels of isolation on minimal board space.  IL710-Series
product details IL710-Series data sheet
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