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We are designing a data link between two boards. It is going to be used in a very rough neigbourhood, inside a power electronics converter, a high voltage motordrive inverter.The distance between the boards just a few meters, but there is going to be severe common mode noise voltages between the boards. We are planning to use Cat5 Ethernet cables, and Ethernet transformers in both ends, in order to handle the common mode voltages.
We cannot use Ethernet PHY, because we must have full control of the encoding and decoding in the FPGA's on each board.
We use this datalink to obtain tight synchronism between the boards. Optical fiber is not an option here, but we are going to use that elsewhere.
Data rate is 100 Mbit/s (Manchester coding => 200 Mbit/s.)
Do you have any suggestions on how to make such a communication link?
LVDS differential signaling would be ideal, but we need isolation transformers due to the common mode voltages in our system. LVDS also use signal level, in the 100 mV region. While we would have signal levels in the 1V range, in order to increase the noise margin.
Emitted noise is not an issue here, immunity is. I have been looking at M- LVDS and PECL transceivers, but I haven't seen any application information where they are used with transformers.
Is it a good idea to use those with transformers?
I have also considered putting two or more M-LVDS transmitters in parallel, in order to beef up the signal level. Is this a good idea?
Which interface devices do you recommend here?
One alternative is to use the CLCL001 as transmitter. It seems to be able to drive cables. The DS90LV001 could be used as receiver.
How would CLCL001 like to see Ethernet transformers in each end of the cable?
We have also looked at DS15EA101 and DS15BA101. Is it a good idea to use such fast devices? How would these like to see transformers in the cable ends?
The datasheet for DS15EA101 says that Transformer coupling is not supported. Why? What is hidden there? How would it work if there were transformers there anyway.
(We are planning to use 5- 10 meter cat5 cable and 1000BASE-T transformers with 1,5 kV insulation, Pulse Engineering HX5004NL We hope that the high insulation voltage will give low capacitance between the windings.)
Any Idea on this?
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