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LMX2592 lock issues

sarath vijayan
Prodigy 80 points

Other Parts Discussed in Thread: LMX2592EVM, LMX2592, USB2ANY

Hi,


We designed a PLL board based on LMX2592EVM schematics. We followed the exact schematics.

But I have issues in getting lock for my board. I used the same test setup for testing this board as LMX2592EVM (we used TICSpro for communication). But I was not getting lock for my designed board and LMX2592EVM was working properly.

When I program my designed board, I can see the current is changing and there are some output but is not same as what I have programmed (plus, the muxout pin is always low)

Can any one think of any problems that could be causing this issue? I have tried to follow the recommendation for layout based on the LMX2592 datasheet.

Thank you for your help in advance.

Regards

Sarath

  • 0
    TI__Expert 4085 points
    Hi Sarath,

    Thanks for your interest in our products. I'm sorry you are having issues with LMX2592.

    Would you be able to provide schematic and layout for your design?

    Thanks,
    Julian
  • 0 in reply to Julian Di Matteo
    Prodigy 80 points

    Hi Julian,

    Thank you your reply. Please find the attached schematics, PCB and gerber file for you to review. Please do let me know if you can what could be the issue.

    Schematics_PLL design.pdfgerbers.zipPCB_PLL design.pdf Regards

    Sarath

  • 0 in reply to sarath vijayan
    TI__Expert 4085 points
    Hi Sarath,

    From the file menu of TICS Pro:
    Can you please provide TICS Pro file or export register settings and attach it?

    Are you using the same exact TICS Pro configuration in the EVM and your board?

    Thanks,
    Julian
  • 0 in reply to Julian Di Matteo
    Prodigy 80 points

    Fullscreen HexRegisterValues.txt Download 
    R64	0x4000AF
R61	0x3D0001
R59	0x3B0000
R48	0x3003FD
R47	0x2F08CF
R46	0x2E0F23
R45	0x2D0000
R44	0x2C0000
R43	0x2B0000
R42	0x2A0000
R41	0x2903E8
R40	0x280000
R39	0x278204
R38	0x260036
R37	0x254000
R36	0x240011
R35	0x23021F
R34	0x22C3F0
R33	0x214210
R32	0x204210
R31	0x1F0001
R30	0x1E0034
R29	0x1D0084
R28	0x1C2924
R24	0x180509
R23	0x178842
R22	0x162300
R20	0x140064
R19	0x130965
R14	0x0E018C
R13	0x0D4000
R12	0x0C7001
R11	0x0B0018
R10	0x0A10D8
R9	0x090302
R8	0x081084
R7	0x0728B2
R4	0x041943
R1	0x010808
R0	0x00221C

  • 0 in reply to sarath vijayan
    Prodigy 80 points
    Hi Julian,

    Please find the TICS pro configuration register in my previous post.
    And yes, I am using exact same configuration for the EVM and my board.

    Thank you very much
    Regards
    Sarath
  • 0 in reply to sarath vijayan
    TI__Expert 4085 points
    Hi Sarath,

    Thanks for providing the files. We are looking into this. One more question, I'm assuming you are using USB2ANY to program LMX2592 on your board. Is this the case?

    Thanks,
    Julian
  • 0 in reply to Julian Di Matteo
    Prodigy 80 points
    Hi Julian,
    Yes. I am using USB2ANY to program LMX2592 in my board and the EVM.

    Thank you. Please let me know if you need any other information that will help you to debug the issue.

    Regards
    Sarath
  • 0 in reply to sarath vijayan
    TI__Expert 4085 points

    Hi Sarath,

    After reviewing the schematic I did not see any obvious issues.

    Do you have R11 and R4 populated on your board? Are you using RFOUTB for Single ended or differential?

    If using differential, I suggest to remove both resistors, since these are 50 ohm resistors for output termination. These resistors are not populated in the EVM. If you are using single ended it's OK to leave the resistor on the unused side.

    Also have you used TP81-83 to check SPI signals are coming out from USB2ANY?

    Here we have a blog for things to try when the PLL does not lock.

    It may be useful for debugging:

    What to do when your PLL does not lock
    Have you ever been frustrated just trying to get your phase-locked loop (PLL) to lock? Premature assumptions can make the debugging process much longer and more tedious than necessary. By following the…
    By in Technical articles > Analog

    Thanks,

    Julian

  • 0 in reply to Julian Di Matteo
    Prodigy 80 points

    Hi Julian,

    Thank you for reviewing the schematics. I have the R11 and R4 populated and I am using ROUTB as single ended. Do I need to only remove the resistor on unused side (or do I need to remove on both + and -)?

    But do you think PLL lock issue is associated to these resistors? I have have checked the SPI signals from USB2ANY and they are fine.

    Regards

    Sarath

  • 0 in reply to sarath vijayan
    TI__Expert 4085 points

    Hi Sarath,

    Sorry for the delayed response. If you are using single-ended, keep the resistor on the unused side. Remove resistor from the used side. (50 ohm termination on unused side)

    Regards,

    Julian