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LMX1204: REFCLK_EN error

Jorge Raven
Prodigy 10 points
Part Number: LMX1204


Tool/software:

Hello,

I am trying to configure an LMX1204 clock buffer via SPI, but I am incapable of setting up the registers that enable the SYSREF signals. I can set the rest of the registers and bits, so I have two issues here:

1 - I want to enable the sysref outputs 0,1,2 by setting the respective bits to 1 in register 0x4. While I can enable/disable the Clock Output bits of all 4 channels I cannot enable the values of the bits of the sysref channels, they always remain 0 no matter what I do. 

2 - Whenever I try to set SYSREF_EN = 1 (reg = 15 = 0x0F bit 8) the chip resets completely cause all registers return to their default values.

Im setting the registers from the highest to the lowest, as indicated in the datasheet. The sysref should be generated internally and in continuous mode.

What might be happening that I cannot enable the sysref outputs? Is there a specific order that I should follow?

Thanks in advance.

Jorge Raven.

  • 0
    TI__Guru** 113350 points

    Hi Jorge,

    Suggest use TICS Pro (www.ti.com/.../TICSPRO-SW) to configure the device and copy the register settings to your software.

    For example, below configuration has SYSREF = continuous 40MHz clock.

  • 0 in reply to Noel Fung
    Prodigy 10 points

    Hello Noel,

    That was my initial approach, but didn't work. My desired setup is as follows:

    So the registers should be:

    R90 0x5A0000
    R86 0x560004
    R79 0x4F0005
    R76 0x4C0000
    R75 0x4B0003
    R72 0x480005
    R67 0x4351CB
    R65 0x416410
    R34 0x220005
    R33 0x216666
    R29 0x1D05FF
    R28 0x1C0A08
    R25 0x19020A
    R24 0x180001
    R23 0x17E04A
    R22 0x16A871
    R21 0x151D00
    R20 0x14FE80
    R19 0x13FE80
    R18 0x12FE80
    R17 0x1107F8
    R16 0x1010A0
    R15 0x0F0B80
    R14 0x0E0002
    R13 0x0D0000
    R12 0x0C0000
    R11 0x0B0000
    R9 0x090010
    R8 0x080130
    R7 0x070000
    R6 0x06C924
    R5 0x05493E
    R4 0x043678
    R3 0x03FF87
    R2 0x020203
    R0 0x000000
    Nevertheless, registers that enable the sysrefs do not work:
    - R4: Will never enable the sysref output, instead of getting value 0x043678 will get 0x043608
    - R15: Writing a 1 to the sysref en bit (bit 7 in 0x0F0B80) will reset the whole chip. 
    What can be the reason for this?
    Kind regards,
    Jorge Raven
  • 0 in reply to Jorge Raven
    TI__Guru** 113350 points

    Hi Jorge,

    I plugged in your configuration file (it is indeed a little bit different from your screenshot) into our eval board, I have all the RF clocks and SYSREF clocks output. Current drawn is about 805mA (excluding the onboard LDOs). Were you not providing enough current to the device?

  • 0 in reply to Noel Fung
    Prodigy 10 points

    Hi Noel,

    Thanks for your response. I think you might be correct and my design might not be able to deliver that much current, but would you make me the favor of testing the following registers setup (that I think are the only ones that need modification in our case) and let me know if you obtain the clock outputs and the sysref ouputs as well?


    R72 0x480005
    R25 0x19020A
    R24 0x180001
    R23 0x17E04A
    R22 0x16A871
    R21 0x151D00
    R20 0x14FE80
    R19 0x13FE80
    R18 0x12FE80
    R17 0x1107F8
    R16 0x1010A0
    R15 0x0F0B80
    R14 0x0E0002
    R9 0x09C010
    R8 0x080130
    R7 0x070000
    R6 0x068000
    R5 0x050000
    R4 0x040078
    R3 0x03F000
    R2 0x020203
    R0 0x000000
    Thanks in advance.
    Jorge Raven.
  • 0 in reply to Jorge Raven
    TI__Genius 12490 points

    Hi Jorge, 

    I will be able to take this into lab first thing tomorrow, and I will confirm whether or not the outputs are as expected.

    Thanks,

    Michael

  • 0 in reply to Michael Srinivasan
    TI__Guru** 113350 points

    Hi Jorge,

    Your register configuration works, current drawn is about 750mA.

  • 0 in reply to Noel Fung
    Prodigy 10 points

    Hi Noel,

    Thank you very much for your support. It isn't working currently on our board, but someone else will take care of the issue now.