• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 32 subscribers
  • Views 215 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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: LMH1219 Don't Lock Upper 40 meter Cable

Ali Nosret
Prodigy 20 points
Part Number: LMH1219
Other Parts Discussed in Thread: LMH1228,

Hello,

I am newer in 4K design. LMH1228 is work and support 60m cable(1694A).I think PCB and Stack up is Ok.

When using upper 40-meter cable (BL1694A), LMH1219 not locked and I don’t have any data.

1. what is your Idea in this problem?

2. Could you tell me how to configuration CTLE?

3.How to configuration of other Input and Output?

4.“EQ Observation Status” register (0x02)  is not stable and data changed 0x41 and 0x45, is that true?

5. "Lock Data Rate Indication" register 0x02[4] lock and unlock. 

Could you give me some advice?

This is block diagram of my design.

Best regards

Thanks

  • 0
    TI__Guru* 93670 points

    Greetings Ali,

    If I understand you correctly, your LMH1219 design is not locking at cable reach greater than 40m. Please below note answers to your questions.

    1). 4K Design pcb layout is very crucial. Imperfect pcb layout may cause return loss issue and result into lower cable reach. 

    1a. Please review LMH1219 pcb layout to make sure your layout is as close to the LMH1219 pcb layout as possible.

    1b. It would be a good idea to get LMH1219 Evaluation Board so you can compare your cable reach setup vs this evaluation board.

    2). LMH1219 is an adaptive equalizer and automatically adjusts the gain to the cable reach attached. Therefor you do not need to adjust the CTLE.

    3). Please refer to the LMH1219 programming guide for details. Please below find a link to this document.

    https://www.ti.com/drr/opn/LMH1219-DESIGN 

    4). Reg 0x02 may change dynamically so it is ok.

    5). Reg 0x02 bits 3 and 4 when set indicate device locked. If these bits are toggling, this means device is going in and out of lock. Potentially this could be due to the high jitter at the input of the CDR block or output of the equalizer. If cable reach is less than data sheet recommended cable reaches, this could be due to the high jitter on the transmitter driving LMH1219 coax input or sub-optimal LMH1219 pcb layout. Please refer to the data sheet application section and LMH1219 EVM pcb layout for pcb layout recommendations.

    Regards,, Nasser 

  • 0 in reply to Nasser Mohammadi
    Prodigy 20 points

    Hi Nasser,

    Thanks for reply my question, I think Edge connector cause this problem and I want to change it. I hope to resolve my problem. 

    Best regards,