• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 33 subscribers
  • Views 484 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMH1219: How to configure adaptive EQ of IN0 to OUT0?

user4822106
Prodigy 100 points
Part Number: LMH1219
Other Parts Discussed in Thread: LMH1218, , SIGCONARCHITECT, USB2ANY

Hi Team,

We use LMH1219 with LMH1218 to drive BNC cable. We find it link down even when we use 2 meter Canare 12G-SDI BNC cable to test with 11.88Gbps.

The test setup is signal input from LMH1219 IN0 (single ended 75Ω) with 2 mete cable to OUT0 (differential 100Ω), and then to LMH1218 IN0 (differential 100Ω) and output with 2 meter cable from OUT0 (single ended 75Ω).

The question is:

1. In register map of datasheet, there is only EQ configuration of IN1, then what about IN0?  We select IN0 to OUT0 and set EQ of IN1 in datasheet, there is no change.

2. In order to increase the driving ability of BNC cable, how should we set with LMH1219 and LMH1218?

3. Is EOM needed to be configured?

Thank you.

 

  • 0
    TI__Guru* 93670 points

    Greetings,

    LMH1219 and LMH1218 should be operational as you have noted. I am assuming you cannot get this setup running at any cable length. Please make sure you have access to the programming guides for both  of these devices. Otherwise, please send me an email with your company email address so we can provide you with access to these documents.

    1). In default mode, IN0 is adaptive and there is no need to configure IN0 equalization setting. Please make sure IN_OUT_SEL pin is either high through 1K ohm or it is floating.

    2). In default mode, your setup should work and there is no need for additional setting. Please make sure you initialize the LMH1218 device as noted in the data sheet. 

    3). EOM is n ot needed to be configured.

    4). Could you please confirm if you can get link up at lower rate like 3G SDI?

    Please take a look to see if you can use SigconArchitect GUI to control LMH1218 and LMH1219 devices. This could greatly help debugging this issue. This GUI uses SMBus interface and you can hook up USB2ANY box to your LMH1219 or LMH1218 devices and we can run this GUI to control the device.

    Regards,, Nasser

  • 0 in reply to Nasser Mohammadi
    Prodigy 100 points

    Hi Nasser,

    We have get the newest programming guides for LMH1218 and LMH1219 from TI. And according to the guides, we have configured LMH1219 adaptive cable EQ of IN0 successfully to run several meters of cable.

    Now we have found that when cable is added to LMH1218 output, the electrical eye diagram has serious deterioration. Now we add 4 meters length cable, it's much worse than 2 meters cable or no cable. What do you think what we can try for LMH1218. The test equipment is Phabrix Qx 12G.

  • 0 in reply to Nasser Mohammadi
    Prodigy 100 points

    By the way, we don't have a USB2ANY box at hand.

  • 0 in reply to user4822106
    Prodigy 100 points

    Hi Nasser,

    We have also saw that you have show the demo to use LMH1218 and LMH1219 to run 100m Belden 4794R. But this cable is connected from LMH1218 OUT to LMH1219 IN.

    There is only 10m cable to connect 12G Video Analyzer to LMH1219 input and 1m cable to connnect final LMH1218 OUT to 12G Video Analyzer input. Does that means when we add the length of these two cables, the performance may reduce a lot.

  • 0 in reply to user4822106
    TI__Guru* 93670 points

    Greetings,

    1). First of all, please make sure there is no de-emphasis on LMH1219 100-ohm output. Also set the amplitude to minimum. Additiionally, make sure you have initialized LMH1218 as noted in the data sheet and programming guide. These settings prevent any potential over-equalization. With these settings, you should be able to operate error free at up to 75m B1694A cable.

    2). Do you have a network analyzer to do input return loss measurement on LMH1219 device? It would be a good idea to make this measurement.

    3). If possible, it would be a good idea to get LMH1219 and LMH1218 evaluation boards. These come with a GUI that can be used to control and debug this issue.

    4). Please check lower data rate cable reach such as 3G SDI using your Phabrix video generator/analyzer. 

    Regards,, Nasser