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DS100RT410 10Gbps retimer availability and application

Other Parts Discussed in Thread: DS100RT410, DS110DF410, DS110RT410, DS125DF410, DS125RT410, DS100DF410EVK

Hi guys,

I submitted this question to TI support, but they directed me to post any support requests here to the forum.

I am trying to use a 20GHz clock rate, 3-bit plus over-range,  ADC from Hittite. The ADC performs 1:2 demux, so the output data stream is 10Gbps.

The ADC uses negative voltage power rails, so the output CML have a negative common mode. I plan to process data from the ADC using Altera Stratix IV GT FPGAs, so these lanes need to be AC-coupled to the FPGA. I'd like to place the ADC on a different board than the FPGA, and connect them together using QSFP+ cabling. The DS100RT410 or any of the redriver devices could be used for this application.

To AC couple the signals from the ADC to any other device requires that the signal coming from the ADC has no DC bias. The ADC has an XOR input port that allows a PRBS pattern to be XORed onto the ADC data, thus ensuring enough data transitions. In the attached diagram, I show how a DS100RT410 could potentially be used as the PRBS source; the ADC 10GHz output clock would be divided to create a 10Gbps 0,1,0,1... data stream and the DS100RT410 configured in lock-to-data mode to be synchronous to the ADC clock. The output would be configured for PRBS mode to 'spread' the ADC data.

Does this design seem reasonable?

Are parts available? I'd like to get 5 to 10 pcs so that I can add them to an ADC test board to see if this is feasible.

Cheers,

Dave

0724.hittite_adc_plus_ti_retimer.pdf

  • David

    I apologize for it having taken so long to get an answer to you, and I'd like to ask that you wait a bit longer as we get the experts huddled together here....

    Mark Sauerwald

     

  • Hi Mark,

    No problem, I'll wait for your response.

    Cheers,

    Dave

  • Hi Dave,

    Looking at your diagram, there are 2 uses for the DS100RT410 device.

    1. Clock/Data generator using 5 GHz input clock
    2. Data retimer on the ADC output

    1. The device should be updated to the DS110RT410 for this configuration. The DS110DF410 supports rates from 8.5 to 11. 3 Gbps while the DS100RT410 device supports just 10.3125 Gbps operation. In order for the device to handle an input clock on the high speed pins, the data search mechanism can be disabled. The output of the retimer can be selected as clock or PRBS data output. Please note that when this signal is mixed with the ADC data, you will need a good way to remove this additional data transitions when analyzing the ADC data content. It sounds like you have an idea on how to achieve this.

    2. Once again if the output data is exactly 10 Ghz, then you will need to use the DS110RT410 device, for the same reason as above. This configuration is the standard mode of operation for the quad channel retimer device.

    Another option is to use the internal PRBS generator on the retimers in blue. The retimers can synchronize the PRBS genertors off the incoming data.

    For both of these use cases, the DS110DF410 device requires AC coupling caps on the inputs and the outputs.

    Please follow up with a TI representative for samples.

    Nate

  • Hi Nate,

    Thanks for pointing out that the DS100RT410 only operates at a fixed frequency of 10.3125Gbps.

    The DS110DF410, DS110RT410, DS125DF410, and DS125RT410 all cover a wider data rate range. The difference in parts appears to be that the DF parts have a DFE block, which I don't think my application requires. You mentioned requesting the DS110RT410, which is a non-DFE part, so that seems reasonable.

    These are all new parts. Are these in production now, or just sampling? Which parts have an evaluation board, or can I get the DS100DF410EVK loaded with an alternative part (given that the parts are pin compatible)?

    By the way, if you go to http://www.ti.com/sigcon and click on the DS110RT410 or DS125RT410 links, you'll find that they are broken. The DS100RT410 data sheet lists the features of these parts, so I have the information I need, but you may want to point out this problem to the web guys.

    Thanks!

    Cheers,

    Dave

  • Hello!

     

    Is a question about DS100RT410 1.25Gbps mode: is a CDR unit lock to 1.25GHz and retimes data or bypassed in this case?

    P.S. I try to pass through DS100RT410 1.25Gbps and 10.3 Gbps data stream - it locket on it (LOCK signal ia high). But I also try 2.5Gbps stream - it work well too (with high LOCK). I slightly confused about it.