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EV-ADF4159EB3Z Eval vtune range


I want to use an ADF4159EB3Z eval board with an external VCO with a vtune range or 0-5 volt for 2400 Mhz RF output.

I've populated the loop filter according to AdiSimPLL spec for the correct PLL and my custom external VCO.

I powered the OPAMP with 15 volt but unfortunately, the vtune output is stuck at 15 volt even if I used a 5 volt VCO spec so it is out of range ?

Not sure what i've done wrong since my loop filter components seem all ok, I don't now what I need to do to reduce the vtune output of the eval board so it can be used with my own VCO ?  


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  • Unfortunately, my evm does not work at all with my external VCO. I tested the VCO alone and it work good. I rebuilt a loop filter according to ADsimPLL for the correct ADF chip, my VCO parameters, OP184 opamp at 5V etc....All supply voltage seem ok. It was supposed to lock according to the software simulation but I don't get any vtune voltage so the VCO is stuck on one frequency and nothing change when I program the chip via the USB software. I'm starting to think that I may have a defective board. 

  • Here're some things to check...

    • the ADF4159 requires RFin power levels between -10 dBm to 0 dBm.  Check your VCO will work with the ADF4159 evb  taking into account cable losses plus 9 dB loss through the splitter and pi attenuator on the eval board.
    • check for a 100 MHz reference signal at "refin".
    • check all LDOs on the eval board are operating correctly.  U2, U3, U8, U10 and U13 provide 3V, 1.8V, 5V, 3V and 3.3V respectively.
    • check you can communicate with the ADF4159.  Use the "Muxout" GUI control to set 0V and 3V on the muxout output pin.  If this works you can set muxout to "N-divider output" and check if the N-divider output is the same as your PFD frequency (100 MHz / R).  You can also use the same technique to check the R-divider output.
    • Check the PFD and charge pump output.  If the ADF4159 is unlocked you should be able to drive 0 and 5V on Vtune by toggling the GUI "phase detector polarity" control between positive and negative.
  • It was an issue with my loop filter. I made some simulation with different VCO and I realized I was using the wrong filter for my VCO parameters !!!!  I replaced the loop filter components and now the PLL lock perfectly and the frequency is dead on !  Thanks