[Moved] USB Isolator with Optocouplers

[amirdiani]

Hey guys,

I am interested in designing a USB isolator using optocouplers, but I don't have a clear idea how to do that.
I believe I need two optocouplers to have a bi-directional data transfer and some kind of SPI-USB converter (maybe MCP2210).
Does someone have any idea how I can build such a circuit to isolate USB?
I couldn't find anything online.

Any kind of help is greatly appreciated.

Thanks,
Ami

 

[KlausST]

Hi,

you could use a FT232 and use optocouplers for isolating at UART RxD, TxD (and flow control pins)


Klaus.

 

[D.A.(Tony)Stewart]

Opto for USB1 only
Otherwise Magnetic for many speeds.
https://www.digikey.ca/product-sear...=0&page=1&quantity=0&ptm=0&fid=0&pageSize=500

 

[KlausST]

Hi,

SunnySkyguy is right if you need a USB to USB connection.

I thought of a USB (host) to ucontroller (device) connection.

Pleas provide more details. Speed, data voltage levels, isolating voltage, what host, what device...

Klaus

 

[amirdiani]

Thank you guys for the replies.
I am using this isolator for an internet device. In a simplified form, that device can be considered an Ethernet to USB adaptor, and the USB port is used to convey the internet data to the computer. The data voltage level is 5V, and I need a connection speed of at least 50 Mbps. As SunnySkyguy have mentioned, I might need to use magnetic couplers rather than opto.

Thanks,
Ami

 

[FvM]

Twisted pair ethernet adapters have built-in isolation, why would you ever need additional USB isolation for a network adapter? The available USB isolators from Analog Devices are for full speed USB (12 MBPS) maximum. High speed USB isolators, if available at all, will be rather expensive.

 

[KlausST]

Hi,

do you want to isolate D+ and D- of the USB lines?
This is rather difficult, because the lines are bidirectional and they need to transmit DC resistance for USB speed setup.

So you need an intelligent solution. Like the AnalogDevices..

Klaus

 

[D.A.(Tony)Stewart]

I hope you understand these ports are quite incompatible and requires conversion at every layer of the OSI model.

A successful solution will convert the bidirectional NRZ half-duplex 180 Ohm differential , DC biased USB to the biphase -trilevel differential separate Rx Tx pairs on CAT 4 100-110 Ohm differential magnetic coupled Ethernet PHY.

Half duplex single to dual channel transceivers are required with clock recovery and generation required for the Ethernet. Then latency and software driver compensation must permit the communication beyond the USB latency limit of 5m. USB3 has the advantage of target initiated communicationvs host polled communication.

If this is beyond the scope of your project an existing solution may be searched, purchased.

keep in mind, CAT5 cable,is ~50pf/m and <3 Ohms/100m, is also important.