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LMK04102 / How to use

Other Parts Discussed in Thread: LMK04102


Please discuss how to use the LMK04102.

Input oscillator is TCXO, frequency is 50MHz.

Output frequency is 800MHz.

In this case, should we use LMK04102 such as figure 15 on the datasheet ?

Please show me if you have another good design.

If there is lack of information, please let me know.

Best Regards,


  • The LMK04102 is a dual loop device. The input comes from a reference into a CLKin port, then the first PLL uses an external VCXO (or TVCXO, VCO, etc. some voltage controlled oscillator) to lock to the reference. PLL1 typically has a narrow loop bandwidth to allow the VCXO phase noise to replace the phase noise of input reference which could be noisy, just not as good as desired, or of a low frequency. This voltage controlled oscillator output is connected to the OSCin. PLL2 then uses the internal VCO to lock to the VCXO to multiply to a high frequency then divide down to each desired output frequency.

    Please refer to figure 12 of datasheet or the EVM instructions/User Guide for example circuit.

    With a 50 MHz TCXO, you may find acceptable performance operating the device in single loop mode, meaning PLL1 charge pump is tri-stated and the TCXO drives OSCin directly.