Can Vtune voltage vary with different populations of ADF4360-2 for the same circuit board?
We have a Modulated RF signal from the DAC (AD9705BCPZ) that feeds into Vtune along with the Charge Pump (CP) Output.
Typically the Modulation shift of the DAC from the carrier frequency for all our previous board assemblies were set between 60 and 65 for a Vtune voltage of 1.5V.
With the latest set of assemblies the Vtune voltage output is now 2.0V and to get the frequency we need we've got to set the Modulation shift of the DAC from the carrier frequency to 85 so as to get the correct frequency output from the VCO.
Is it typically for the part to have such a large change in its voltage to frequency slope. I am particularly interested in a more detailed explanation and understanding or figure 14 of the datasheet between 1900MHz and 2000MHz. We use the divide by 2 option of the ADF4360-2.