SNAS783C June 2020 – February 2021 LMX2820
PRODUCTION DATA
The frequency doubler is used to produce an output frequency that is twice the VCO frequency and is selected when OUTx_MUX = 2. When the VCO frequency is doubled, the fundamental (non-doubled) VCO frequency does leak to the output and this is the sub-harmonic (0.5X). To minimize these sub-harmonics, there is tunable filter that tracks the output frequency and filters out this sub-harmonic as well as other undesired harmonics (1.5X, 2X, 3X, ...). The calibration for this tunable filter is automatically triggered whenever the VCO calibration is done.