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.

DS90UB947-Q1: DS90UB947-Q1 RE Test issue

Part Number: DS90UB947-Q1

Hi,

We make RE test for DS90UB947-Q1,Result:below standard at 450MHz,The picture is waveform for result。Please share me some improved method,Thanks a lot!

  • Hi,

    The simplest way would be to use a REFCLK that has spread spectrum capability.  0.5 % spreading with triangular modulation at about 30kHz should do the trick.  SiTime 9005 series has worked for me in the past.

    Other alternatives:

    • Cover the shield box seam with copper tape. Cover the cable entry point with copper tape, extending 0.5” onto the cable.

    • Adjust the bend radius of the cable as it makes the turn from the 1 meter straight segment to connect to the shield boxes.

    • Try a higher performance cable.  Only use new cables with less than 10 connector insertions.

    • Try different shield box positions and orientations.

    • Try different DC cable routing and cable lengths. Generally shorter is better, but exceptions to that have been observed.

    • Many standards allow a clamp-on ferrite on the DC power cable inside the shield box.

    Mike

  • Hi,

    How to use a REFCLK that has spread spectrum capability.Can you describe it in detail?Thanks a lot!

  • Hi,

    In my reference designs I use a 2mm x 2.5mm clock.  When I want  a SSC, I order from Epson or SiTime or similar.  They have the standard footprints; all you have to do is replace your clock with their SSC.  No PCB layout changes if you use a standard size and pinout.

    VDD: 1.8V

    Size: 2mm x 2.5mm

    Spread type: Downspread and Triangular

    Spreading rate: about 30kHz

    Spread %: 0.5

    If you talk to their apps engineers they can get you a part number based on your requirements, and also get you samples to test.

    Mike

  • Hi,

    Where can I get your reference designs?

  • Here is the 947 user guide with schematics:

    Here is the 953 user guide with the 2mm x 2.5mm REFCLK:

    Mike