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Galvanic isolated 1 Channel LVDS - possible to use TLK1221 with 1000BaseT ethernet transformer ?

Wolfgang Ebersbach
Prodigy 20 points
Other Parts Discussed in Thread: TLK1221, TLK1501

Dear all,

for a medical application, I must get an 8 bit parallel bus that serves up to 20 MBits/sec, trought a long cable (somewhere in between 3 and 7 meters) to another 8Bit bus that acts as receiver. This is unidirectional Additional, I need 2 control bits in the same direction and 6 in the other direction. 
To make it not so easy, this entire thing must provide galvanic isolation between the two busses. I could of course use digital isolators on the bus side, but then I would need 16 isolation channels which will end up in with at least 4 expensive isolator IC's.
 As I need this 4 times in parallel, it would summ up to 16 ADUM or similar isolators.

Now, I came up with the idea of using an TLK1221 and isolate its LVDS IO's with an 1000BaseT Transfomer. BUT the are no hints in the datasheet if this is possible. Has anyone ever done such thing or any alternate ideas ?

This guy has more or less the same idea / question: http://e2e.ti.com/support/interface/high_speed_interface/f/138/t/190603.aspx but I would stick with PULSE H5084NL transformers.

Reagrds,

  Wolfgang Ebersbach

  • 0
    TI__Expert 7850 points

    Wolfgang,

    Please note that the TLK1221 does not support 20Mbps data rate.

    Typically a transformer is used with 1000BaseT Ethernet.  If the customer is looking for 10/100/1000BaseT support then TLk1221 will not work as it supports a different 1G Ethernet standard for back plane and optical links.  If a transformer is simply being considered for isolation, then please make sure it can actually support data rates that the serdes device can support i.e. 600mbps to 1Gbps+.

    Assuming the applications data rate can be increased, you can create a point to point link to transport two 8bit bytes by using a device like TLK1501 which supports a 16bit wide parallel interface that can accommodate the application.  TLK1221 supports 10bit parallel interface but this assumes that the 10bits are already 8b/10b coded.

    Thanks,

    Atul Patel

  • 0 in reply to Atul Patel
    Prodigy 20 points

    Atul,

    I know that TLK1221 does not support 20MBps data rate. But I can transmit every byte multiple times, so what.
    I do not intend tu use xxBaseT. I only intend to transmit raw bits over a cable without having to use a 16core cable. And to isolate all this.
    I originally looked at the TLK1501, but this is tripple the price as the TLK1221.

    So. the only remaining question is, if the output drivers / input stages of the TLK1221 is able to work with an transformer. As noted, I would use an 1000BaseT transformer, which should be able to do the lowes possible data rate af the TLK1221 which seems to be 0.6 Mbps

    On the other hand, if you can confirm that TLK1501 can work with a transformer, I may use that one.

    Thanks,

        Wolfgang

  • 0 in reply to Wolfgang Ebersbach
    TI__Expert 7850 points

    Wolfgang,

    As long as the transformer is rated for the needed frequency, then a device like TLK1221 should be able work with it.

    Also, as mentioned earlier, using TLK1221 assumes the parallel data is already 8b/10b coded so your application will have to take that into account.

    Thanks,

    Atul