isolated USB

I researched this some time ago and making an isolated USB converter is no simple task. For one thing, the host side will have to supply the 5 VDC to the client side and also mirror the current draw upon connection and configuration. And the signal lines are bidirectional, high speed, and must have matched propagation characteristics. Here is an article I found about three years ago:

But here is a press release from EDN about a USB isolator just made available recently:

I see that's what you had in mind that costs $99 from Mouser. And that may be a reasonable cost if you need to maintain transparency so that the isolated device enumerates and works in the same way as it would by direct connection.

Otherwise, it is better to isolate the circuit based on its functionality. USB is basically a serial protocol with packets being sent and received with status and data information. If you are working at that level, it may be possible to use USARTs with just TxD and RxD lines through a digital isolator such as SiLabs SI844x, which costs just a few dollars, depending on speed. There are other peripherals which may work using SPI, which can be isolated.

Searching more on the EDN site I found this single-chip solution ADuM4160 from Analog Devices for about $5 (and an evaluation board from AD for $55):

Paul

I did find the Analog part ADum4160. I'll bookmark that for future reference. But right now I'm looking for something like the keterex box or even a cable with it built in.

Cheers

Check

Don

Picked up the Keterex, full speed. Uses the Analog Devices icoupler chip. Have a picture of the guts if anyone is interested.

Cheers