Fractional-N synthesizer for RF local oscillators
The LTC6948IUFD-2#PBF is a fractional-N PLL frequency synthesizer from Analog Devices, designed for RF/IF local oscillator generation in wireless infrastructure and test equipment. It integrates a phase-locked loop with a voltage-controlled oscillator (VCO) core, delivering a maximum output frequency of 4.91 GHz. The fractional-N architecture allows fine frequency step sizes without requiring a high reference frequency — a practical advantage when the reference is a fixed TCXO or ovenized crystal.
Wide supply and industrial temperature rating
The supply voltage range spans 3.15 V to 5.25 V, covering both 3.3 V and 5 V rails common in baseband and RF boards. The 28-QFN package with exposed pad (4x5 mm) provides a low-inductance ground path for the VCO and PLL charge pump — critical for phase-noise performance above 3 GHz.
Active production, tube packaging
For production quantities, the reel-packaged variant (LTC6948IUFD-2#TRPBF) is the common tape-and-reel alternative — confirm the BOM line's packing specification before ordering.
Differential I/O and single-circuit PLL
Both the input and output are differential, which helps reject common-mode noise on the reference and output paths — important when routing the synthesizer output across a mixed-signal board to a mixer or ADC clock input. The PLL is a single-circuit device with a 1:1 input-to-output ratio, meaning one reference drives one synthesised output. The divider/multiplier block is present on the feedback path to support fractional-N division ratios.