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Internal Clock for ADC12D1800RB

G L1
Prodigy 30 points
Other Parts Discussed in Thread: ADC12D1800, LMX2531, LMX2541, CODELOADER, USB2ANY

Hi,

Is there a way to change the internal clock of adc12d1800 board into a different frequency other than 1.8 GHz? Is it possible to set the internal clock to 1.2GHz? Thank you

  • 0
    TI__Genius 13335 points

    Hi,

     It depends which version you have. There have been several iterations of the eval board which made various changes and improvements. There are two quick methods to determine which you have.

    You can open WaveVision and see what FPGA image is being loaded. It is displayed once at startup and all the time at the top of the window (shown below).

    Here I'm showing version 2 of the board. ADC12D1600RB2. We can use this number to determine which clock is installed.

    Or you can also inspect the board and read the top side mark of the clock device directly shown below.

     

    You can enter this information into the part marking tool which will translate it to the corresponding device: http://focus.ti.com/general/docs/partmarking/partmarkinghome.jsp

    The two clocking devices we have used are the LMX2531LQ1778E or the LMX2541SQ3740E.

    The available VCO frequencies are limited to the following: 

    Clocking Device

    VCO Frequency (MHz)

    LMX2531LQ1778E

    1726 – 1840

    LMX2541SQ3740E

    3480 – 4000

     The LMX2531 is run at 1800MHz and outputs the VCO directly. It has the option to use the output divider of /1 or /2. If this is the version you have then you cannot output 1200MHz.

    The LMX2541 is run at 3600MHz and uses the output divider to get 1800MHz. The output divider has a much greater range, /1 to /63. We currently use /2 to get 1800MHz. If you use /3 you can get to 1200MHz.

     Note that you cannot program the clock directly from the WaveVision GUI though. You will either need to modify the XML script file and/or FPGA image or you will need to use an external microcontroller like USB2ANY and connect it directly to the SPI bus and program using CodeLoader.

     An easier method is to configure the board for external clock and connect a 1200MHz clock source directly. Again depending on which version of the board you can either change it directly in WaveVision, or it may require a resistor change in addition to setting it in WaveVision. Please refer to the following thread: http://e2e.ti.com/support/data_converters/high_speed_data_converters/f/68/p/304442/1060429.aspx#1060429

     Let me know how it goes!

  • 0 in reply to Luke LaPointe
    Prodigy 30 points

    Hi,

     I am using the ADC12D1800RB2 board.

    On the ADC 1xDxxxx(RF)RB User's Guide, it says that you can control the clock on WaveVision 5

    I'm really confuse with it. So, which one is the correct one?

    Also, when I tried to connect the external clock to the board, I noticed that the board does not recognize the clock. The data sheet and the user guide state that you just need to change the setup on wavevision 5 into the external clock, however I did not find this to be working. I also noticed there are many discrepancies between the picture on the website with the board that I have.

  • 0 in reply to G L1
    TI__Genius 13335 points

    Hi,

    That sentence is misleading, I think it should read: 

    “On the ADC1xDxxx(RF)RB board, the clocking device is configured for a frequency in this range in an xml script file and written over the SPI interface when the FPGA image is loaded. For convenience jumpers, J158 – J162, have been added so that when removed the clock is disconnected from the FPGA, allowing direct SPI writes with an external programming device to the clock."

    And this sentence should be added to the following paragraph for RB2 versions of the board:

    "If external clocking is desired, the device may disabled through the WaveVision 5 register control panel in addition to changing the position of R180 from B to A"

    See the following thread for more information on how to modify the board for external clocking: http://e2e.ti.com/support/data_converters/high_speed_data_converters/f/68/p/304442/1061353.aspx#1061353