Is it possible to replace the VCO with an OCXO on the ADRV9009-ZU11EG on ADRV2CRR-FMC

Question

Hi, we have a high frequency application requiring tight frequency stability. To minimize drift: 
 
 Can we simply replace the on board SoM VCXO with an OCXO? 
 We see an reference input on the SoM and CRR boards but those paths appear to require a VCXO at the HMC7044 OSCIN. This appears to make it pointless to use an OCXO as a reference or have we misunderstood how the HMC7044 outputs are generated when provided and external reference? 
 If option 1 is not possible, what is the recommended way to minimize frequency temperature drift? 
 What is the onboard TCXO used for? And would that need to be replaced with an OCXO as well? 
 
 Your assistance is highly appreciated.

RR4 · Accepted Answer

1. You can't replace the VCXO with an OCXO, charge pump out is coming from HMC7044 and controlling the frequency of the VCXO, another thing is note is the VCXO part used in the design is an ultra-low-noise phase oscillator, and not sure what kind of part are you planning to use. 
 2. For HMC7044-related questions please open a new post with specific questions in the below forum. 
 https://ez.analog.com/rf/ 
 3. What is your requirement for frequency drift? were you able to measure the drift with the existing design? 
 4. PLL1 accepts up to four references and one of them is getting from TCXO, please refer to the HMC7044 datasheet PLL1 Reference inputs section for more details.)

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Is it possible to replace the VCO with an OCXO on the ADRV9009-ZU11EG on ADRV2CRR-FMC

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