LMX2581: Spurs at output

Hello Roni,

3.0 V is below the recommended input voltage of 3.15 V, so I wouldn't recommend it.  If you increased your voltage from the DC/DC, then used an LDO that could work.  Obviously you need enough headroom.  Note there is already an LDO on the VCO.

As to whether the VCCVCO supply pin is the vector for the spurs, try reducing the PLL loop bandwidth - if the spurs are attenuated then it is impact an PLL supply such that the loop filter is filtering these spurs.  If increasing the PLL loop bandwidth reduces the spurs, then it may be the VCO pin.  It may be difficult to increase the loop bandwidth and see if the spur is reduced if the PLL noise obscures it.

73,
Timothy