Hi, I am using AD9520-1 BCPZ IC for getting 12 , 250 MHz differential clocks. In this case I have left open the pin no. 63 and 64 i.e. REF1 and REF 2 and giving an differential input clock of 100 MHz at pin no. 13 & 14. Loop filter input is coming from charged pump output through Loop filter and connected at pin no.9 i.e. loop filter pin. This IC is working in three different modes, I am not able to get which mode I have to use and how to get 250 MHz output. I have attched the reference schematic also.