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LMK5B33414: Selection of LVDS and LVPECL

Gaofeng Zhao
Prodigy 90 points
Part Number: LMK5B33414
Other Parts Discussed in Thread: LMK00308,

Tool/software:

Hi Clock team,

I am currently working on the design of a high-precision clock system for a diagnostic ultrasound instrument. For this project, I have selected Texas Instruments' LMK5B33414 as the clock source and the 3-layer LMK00308 clock buffer chip to distribute the clock signal throughout the system.
Regarding the connection between the LMK5B33414 and the first layer of the LMK00308, I have chosen to use LVPECL signaling on the PCB to leverage the optimal output characteristics of the LMK5B33414. After comparing the two output level standards using an oscilloscope, LVPECL has proven to be significantly superior in performance.
For the subsequent layer-by-layer output distribution of the LMK00308, the signal will travel approximately 1 meter through cables and an additional 50 cm on the PCB board. I am uncertain whether to continue using LVPECL or switch to LVDS for this part of the transmission.
I have a few questions that I hope you can help me with:
  1. Does the LMK00308 support conversion from LVPECL to LVDS?
  2. If I switch to LVDS, will the signal quality degrade to the level shown in the second graph below?

  3. Is there a recommended solution?

Best,

Gaofeng

LVPECL output form LMK5B33414EVM，25M JESD SYSREF and 125M AFE sample clock:

LVDS output form LMK5B33414EVM，25M JESD SYSREF and 125M AFE sample  clock

 

  • 0
    TI__Mastermind 22400 points

    Gaofeng,

    1. LMK00308 is able to accept an LVPECL input and output LVDS clocks.
    2. The swing level of LVDS is much lower than the LVPECL swing. The RMS jitter will be higher for the LVDS output format due to the higher swing of LVPECL.
    3. Do you have the specifications for the clock receiver that you can provide?

    Thanks,

    Kadeem