LMK04102 / How to use

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.

73,
Timothy