Dear Sir

Will the ADF4159 reference doubler work with reference inputs of 250MHz? I have a low phase noise 250MHz signal and I would like to use it as a reference for the ADF4159. Additionally I would like to optimize the phase noise of the PLL system, so would like to use the PFD at 100MHz. Can I double the 250MHz reference to 500MHz and then divide by 5 to get to 100MHz PFD frequency? By the way my evaluation ADF4159 on your eval board does not seem to let me do this. Is this to be expected? What's a sensible way to optimize the phase noise of my system? Just use the 250MHz reference and divide by 3 to get to an 83.3MHz PFD frequency and not use the doubler?

Best regards

John

When using the reference doubler, the maximum reference input frequency is 55 MHz. This will be in the final data sheet.

For your situation, either use the 83.3 MHz PFD frequency, or use an external divide to get 50 MHz and then use the on-board doubler.