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LMH1297: SDI_IO Cable Equalizer Settings

Masaru Tamai
Prodigy 235 points

Part Number: LMH1297
Other Parts Discussed in Thread: SIGCONARCHITECT

Hello.

May I ask you about Cable Equalizer ?

We have a problem with some output devices that do not lock when connected with a 1m cable.

(The other receivers are receiving successfully.)

When we set the Cable EQ Bypass setting or extend the cable to about 10 meters, it locks, so we think the problem may be caused by the EQ setting.


We are hoping to resolve this issue without using the Cable EQ Bypass.

Do you have any good advice?

Conditions

Signal : 12G-SDI

Device : LMH1297

register value :

EQ Observation Status (0x01) - eq_bypass_status (bit3) : 0

EQ Observation Status (0x01) - adaptation_status (bit0) : 1

Cable EQ Index (0x25) - CEI : 0x03

Best Regards,

  • 0
    TI__Guru* 93570 points

    Hi Tami-San,

    Please contact your TI quality people. Based on your test, this device does not operate as expected. With cable EQ index of 0x25=0x03 we should be running error free. It seems somehow this device has gotten damaged.

    Regards,, Nasser

  • 0 in reply to Nasser Mohammadi
    Prodigy 235 points

    Dear Nasser

    Thank you for your reply.

    If I stretch the cable or cool it down it will lock up, but is the device itself damaged?

    Sorry. I will add the information we have.

    -This symptom can be remedied by cooling the LMH1297 down. (The LMH1297 will lock up and output a screen.)

    -This problem also occurs on other boards.

    -There are devices on other boards that are repeatedly locked and unlocked.

     (The device is completely unlocked when heated and locked when cooled.)

    We think that the CDR is not able to lock in the EQ settings.

  • 0 in reply to Masaru Tamai
    TI__Guru* 93570 points

    Greetings,

    1). On the board that you are seeing this problem, can you please try to re-solder 75-ohm high speed signal path. Do you still see this issue?

    2). What is the signal launch amplitude? Do you see a difference if you change launch amplitude?

    3). Please use SigconArchitect GUI to record register settings and send us register content when device is locked versus when it is not locked.

    Regards,, Nasser

  • 0 in reply to Nasser Mohammadi
    Prodigy 235 points

    Dear Nasser

    Thank you for your reply.

    1). On the board that you are seeing this problem, can you please try to re-solder 75-ohm high speed signal path. Do you still see this issue?

    ->The problem occurs even after re-soldering the board.

    2). What is the signal launch amplitude? Do you see a difference if you change launch amplitude?

    ->This does not occur when the cable is extended to attenuate the waveform.

    3). Please use SigconArchitect GUI to record register settings and send us register content when device is locked versus when it is not locked.

    ->We are unable to use the SigconArchitect GUI on our board. I'm attaching the data recorded with our prepared software.

    Best regards, 

    LMH1297_lock vs unlock.xlsx

  • 0 in reply to Masaru Tamai
    TI__Guru* 93570 points

    Greetings,

    Thanks for sending us register dump for when device is locked versus when it is not lock. 

    1). Can you please let us know if you used two different cable lengths? One shows EQ index ConfigIO reg.0x25 =0x05 and another shows the same register with a value of 0x03. 

    2). You noted if you bypass the EQ, then we can run with no bit error? Can you please confirm. 

    3). I am assuming this occurs just at 12G data rate?

    Regards,, Nasser

  • 0 in reply to Nasser Mohammadi
    Prodigy 235 points

    Dear Nasser


    Thank you for your reply.

    1). Can you please let us know if you used two different cable lengths? One shows EQ index ConfigIO reg.0x25 =0x05 and another shows the same register with a value of 0x03.

    -> Lock (0x05) = 10m cable , Unlock (0x03) = 1m cable
     

    2). You noted if you bypass the EQ, then we can run with no bit error? Can you please confirm.

    -> Yes. Lock when the EQ is set to the bypass setting.

    3). I am assuming this occurs just at 12G data rate?

    -> Yes. The problem occurs at 12G data rates. Lock at 6G data rate.

    Best regards,

  • 0 in reply to Masaru Tamai
    TI__Guru* 93570 points

    Greetings,

    With 1m cable length and EQ index of 3 - based on the data you had sent - device should be operating normally. I think it would be a good idea to send one of these devices for failure analyses so we can investigate further. How many devices fails with this symptom?

    Regards,, Nasser

  • 0 in reply to Nasser Mohammadi
    Prodigy 235 points

    Dear Nasser


    Thank you for your reply.

    The device from which the registers were obtained is symptomatic even at room temperature.

    This symptom occurs on all LMH127 on our board when heat is applied.

    If the ambient temperature is around 40 degrees Celsius, symptoms are sure to occur.

    Is there anything we can analyze without sending the device?

    Best regards,

  • 0 in reply to Masaru Tamai
    TI__Guru* 93570 points

    Greetings,

    Can you please let me know what is the 1m cable model you are using?

    Regards,, Nasser

  • 0 in reply to Nasser Mohammadi
    Prodigy 235 points

    Dear Nasser


    I use the following cable and plug combination.

    Plug : BCP-D55UHD

    Cable : CANARE L-5.5CUHD


    The model number of the CD on the source side has been found. However, I can't publish it. How should I contact you?


    Best regards,

    How should I contact you?

  • 0 in reply to Masaru Tamai
    TI__Guru* 93570 points

    Greetings Tamai-San,

    We have field application engineers responsible for your area. I am checking and will let you know this coming Monday.

    Regards,, Nasser

  • 0 in reply to Masaru Tamai
    TI__Guru* 93570 points

    Greetings,

    TI FAE is in contact with you and already send me cable driver eye diagrams that you had sent. Cable driver may not be meeting SMPTE requirements. I will send this email to TI FAE in your area for further discussions. 

    Regards,, Nasser