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LMK03328: The same frequency between Input and Output which conditions are 25MHz to 500 MHz with granular of 1 MHz

Hirotaka Matsumoto
Guru 27585 points
Part Number: LMK03328

Hi all


Would you mind if we ask LMK03328?
 

We consider implementing a jitter cleaner using LMK03328 which output the same frequency as its input.

The input frequencies are something between 25MHz to 500 MHz with granular of 1 MHz.

We confirmed that LMK03328 can realize it, however I have one question.

 

<Question1>
Can you let me know, if one external capacitor value for the loop filter can support all frequencies?


<Question2>
Please also let me know if internal filter components can realize all frequencies?

Kind regards,

Hirotaka Matsumoto

  • 0
    TI__Expert 6140 points

    Hi, 

    I'm assuming different configurations are being generated / used for each case? As in one use case will be 25 MHz input, next 50 MHz, etc. 

    To answer question 2 first, yes. The LMK03328 should be able to support all frequencies as long as you stay within the VCO frequency range. Internal filter components should not have any issues. 

    On question 1, I would anticipate one loop filter capacitor would be able to support all frequencies, but that depends on if PLL bandwidth is changing for any of the configurations to support the frequencies. 

    Here's the note from datasheet section 10.4.10:

    It is important to set the PLL to best possible bandwidth to minimize output jitter. A high bandwidth (≥ 100 kHz) provides best input signal tracking and is therefore desired with a clean input reference (clock generator mode). A low bandwidth (≤ 1 kHz) is desired if the input signal quality is unknown (jitter cleaner mode). TI provides the WEBENCH Clock Architect that makes it easy to select the right loop filter components.

    Here's also an E2E thread on PLLatinum sim software that can be used to create / simulate loop filter settings: 

    https://e2e.ti.com/support/clock-and-timing/f/48/t/878803?keyMatch=LMK03328&tisearch=Search-EN-support

    Thanks and regards, Amin