SNAS783C June 2020 – February 2021 LMX2820
PRODUCTION DATA
The LMX2820 requires an external loop filter that is application-specific and can be configured by PLLatinum Sim. For the LMX2820, it matters what impedance is seen from the VTUNE pin looking outwards. This impedance is dominated by the component C3 for a third order filter or C1 for a second order filter. If there is at least 1.5 nF for the capacitance that is shunt with this pin, the VCO phase noise will be as close to the best it can be. If the capacitance is less, the VCO phase noise in the 100-kHz to 1-MHz region will degrade. This capacitor should be placed close to the VTUNE pin.