According to the data sheet, the output common mode voltage of the ADRF6518 is set by the voltage at pin 20 of the device.
We have this pin driven from an opamp buffer at 1.5V (I have checked the voltage actually at pi 20 is 1.5V) however, the output common mode voltage is 1.27V (with no ac signal component). The current from the output pins is 1.45mA so is not loaded enough to account for this low output voltage.
The supply voltage is 3.25V.
I can't see any reason for this 230mV discrepancy, which will reduce the devices output swing.
What am I missing ?