I have an industry LAN application where high isolation is required (6KV tests). When I searched the web I hardly found any magnetics that isolation would be higher than 2KV. There is Hallo with SMD 4.5KV 10BASE-T ISOLATION MODULES (https://www.haloelectronics.com).
If someone knows for better modules, please let me know
best regards,
cruix
One way to increase the voltage difference is to put two or more transformers 1:1 in tandem. Then use a resistor divider chain to put the center taps at equal voltage increments. This keeps the common mode voltage across each one in specification. The resistors will have to be high voltage rating or several lower voltage rating in series. They should be high enough in value to not become overheated by the worst case voltage differences. This will slightly degrade the frequency response which probably will not affect your error rate much.
I have looked at sites you recomended, but 2kV is most what they have. Last week I was talking to sales manager from Pulse (Phillipe), and he told me that it will be hard to find even 4kV isolation magnetics. But I know that there was some parts made, for industry application where 6kV was needed.
Yes I have already thought about two transformers in series, but PCB space is also critical.
For now I stay with Hallo 4.5kV magnetics.