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WEBENCH® Tools/LMK04208: clock design tool(http://www.ti.com/tool/clockdesigntool)

Waldner Wu
Prodigy 60 points
Part Number: LMK04208
Other Parts Discussed in Thread: LMK04828, LMX2594

Tool/software: WEBENCH® Design Tools

Hi, Teams:

I has followed LMK04208 user guide to download “clock design tool”(http://www.ti.com/tool/clockdesigntool).

I can’t find out LMK04208 in “Select Solution page”.

If I use “LMK04828B_VCO0” to simulation loop filter and phase noise performance, is it OK?

Best regards,

Waldner

  • 0
    TI__Mastermind 30910 points

    Hello Waldner,

    I believe LMK04828 VCO1 is the better choice for loop filter simulation. LMK04208 VCO is about 2dB lower performance than LMK04828 VCO1, and the frequency range of the LMK04208 is a much closer match (2750-3072MHz for LMK04208, vs. 2920-3080MHz for LMK04828 VCO1; LMK04828 VCO0 is 2370-2630MHz, which has no overlap with LMK04208 ranges).

    Regards,

  • 0 in reply to Derek Payne
    Prodigy 60 points

    Dear Derek:

            I am sorry that I didn't describe detail purpose about using LMK04208.

    1. I use LMK04208 PLL1 function for 10MHz OCXO cascade 100MHz VCXO and then  the OSCout 100MHz is for LMX2594 reference clock.

    2. I use LMK04208 PLL1 function for 100MHz OCXO cascade 100MHz VCXO and then  the OSCout 100MHz  is for LMX2594 reference clock.

    If I use “LMK04828B_VCO0” to simulation PLL1 loop filter and phase noise performance, is it OK?

    Best regards,

    Waldner

  • 0 in reply to Waldner Wu
    TI__Mastermind 30910 points

    Waldner,

    I don't think this is valid, because the LMK04828B_VCO0 data was specific to the internal VCO of LMK04828. The 100MHz VCXO will have significantly different performance than the LMK04828B_VCO0, depending on the manufacturer and the quality of the device.

    Based on the datasheet characterization, the LMK04208 charge pump is approximately equivalent performance to the LMK04828, so the PLL characteristics should be comparable. But again, without VCXO data from the vendor, it will be hard to predict performance, and using the LMK04828 VCO data would give very misleading results.

    Maybe it would be be better to use a newer tool like PLLatinum Sim. When used in advanced mode, PLLatinum Sim includes the capability to simulate reference noise (so you can model the 10/100MHz OCXO), insert your own parameters for the VCXO noise based on vendor datasheet values, modify the loop filter components and simulate the effects, export and import traces for comparison or modeling of reference noise in cascade configurations, etc. PLLatinum Sim does not support the LMK04208, but it does support the LMK04828 which has roughly the same performance with PLL1. You could simulate the OSCout performance data using LMK04828 PLL1 performance as a close estimate, export the trace data from PLL1, and import the exported data as a reference input trace for LMX2594.

    Regards,