Joe,
I think you'll need more than a transformer for USB.
IIRC the USB is mostly differential mode - but special codes are
signalled by common mode signals. In addition, the initial hanshake is
carried out at full (or low) speed with the D+ (or D-) line pulled
high with a 1k5 resistor. For high speed, this resistor has to be
disconnected.

Richard P

On 28/06/06, Joe Mailer <maildmx@yahoo.es> wrote:
> Very interesting couplers.
> But these go up to 150 Mbps transfer rate. What about isolating a usb2.0 =
line at 480 Mbps ? I might have to do so with a small 1:1 transformer, any =
good reference ?
>
> Thanks !
>
> William Bross <wbross@cinci.rr.com> escribi=F3: So does the si844x series=
 couplers from http://www.silabs.com
>
> Bill
>
> Joe Mailer wrote:
>
> >iCouplers from analog claim to be bidirectional.
> >
> >Steve Smith  escribi=F3: A transformer is naturally bidirectional you ne=
ed two optos
> >Just a thought !
> >Steve
> >
> >-----Original Message-----
> >From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf=
 Of
> >Joe Mailer
> >Sent: 21 June 2006 18:27
> >To: Microcontroller discussion list - Public.
> >Subject: [EE] A<--> Optoisolators (comm) <--> B
> >
> >Hello,
> >
> >I have two systems A and B. I'd like to have a robust optically isolated
> >communication line (going real time). I have choose RS-232/422/485 as
> >possible communication protocols.
> >
> >I have been searching the net for optoisolators, there are a huge amount=
 of
> >those, but thinking that communication is bidirectional and it could be
> >fast, what are more suitable optoisolators for doing such a thing ? I ha=
ve
> >been looking to (new) analog iCouplers[1], those look good, but i need g=
ood
> >MTBF and good support in the future.
> >
> >Any other good idea ?
> >
> >Thanks !
> >
> >[1]
> >http://www.analog.com/UploadedFiles/Product_Highlights/61991380562796339=
7963
> >229iCoupler_Brochure.pdf
> >
> >
> >
> >
>
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