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As far as I understand the RMII output signal of an ethernet PHY is a TTL signal (at least according to wikipedia). I need to convert these into LVPECL signals. So on the one side I have something like TX0 and TX1 from the RMII and on the other side I have Tx- and Tx+ for the LVPECL interface. How can I interconvert these signals (also LVPECL to TTL)? I found the MAX9370 TTL/LVPECL translater but wouldn't TX0 then split into two signals (same with TX1)? So i would end up with a four signal output from the MAX9370 translater. But I only need two signals as LVPECL input. I think I'm missing something important here.

UPDATE:

Some more details: the phy of interest is the LAN8720. According to the datasheet the RMII outputs LVCMOS signals. These should be converted to LVPECL signals in order to serve as an input for an optical transceiver. My goal is to build a media converter.

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  • \$\begingroup\$ As far as I remember RMII was a mess between HP and 3Com de-facto implementations and not an actual standard as Wikipedia claims. Look in some TI datasheets for PHY for details. \$\endgroup\$ – Fizz Nov 2 '15 at 22:10
  • \$\begingroup\$ The signal levels at the phy are whatever the datasheet says they are. Not going to be ttl, which is a 5v standard anyway, and I bet your RMII phy doesn't have 5v I/O. What are you actually trying to connect the phy to? \$\endgroup\$ – user1844 Nov 2 '15 at 23:47
  • \$\begingroup\$ Seems wikipedia was wrong. I updated my question and added more details. \$\endgroup\$ – user90660 Nov 3 '15 at 11:04
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Curious about the application, but as regards the actual conversion question I've had great luck with On Semi's range of stuff for clock distribution.

I use it for generic differential to single ended stuff all the time, it's not just for clocks. They've probably got a signal converter for ya:

http://www.onsemi.com/PowerSolutions/parametrics.do?id=648

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  • \$\begingroup\$ I updated my question. It seems like they have some devices which could do what I need. In particular, the MC100EPT26 gathered my attention since it should do a 1:1 conversion of TX0, TX1 to TX+ and TX-. But the output is LVTTL and LVCMOS is required in my case. Do you know, if this device also works in the reverse direction? On the other end of my media converter I need something which turns the LVPECL signals into LVCMOS signals. \$\endgroup\$ – user90660 Nov 3 '15 at 11:21
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The Maxim LVPECL converter generates a differential signal, yes you will have 2 differential signals for TX0 (TX0+, TX0-) and TX1 (TX1+, TX1-). If you wish to have only a single pair, you will have to serialize the two bits data into a single stream and then convert to LVPECL.

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  • \$\begingroup\$ How can this be accomplished? \$\endgroup\$ – user90660 Nov 3 '15 at 11:22
  • \$\begingroup\$ You will have to add some logic to do that. There are off the shelf media converters and 100baseFX PHY devices. \$\endgroup\$ – Lior Bilia Nov 3 '15 at 14:19

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