ADF4196 Fractional-N PLLs Frequency Synthesizers

Analog Devices Inc. ADF4196 Fractional-N PLLs Frequency Synthesizers implement local oscillators (LO) in the up-conversion and down-conversion sections of wireless transmitters and receivers. The ADF4196 design meets the GSM/EDGE lock-time requirements for base stations. The fast settling capability makes the ADF4196 well-suited for pulse-Doppler radar applications. The design includes a low-noise, digital phase frequency detector (PFD) and a precision differential charge pump. Analog Devices ADF419's differential amplifier converts the output of the differential charge pump to a single-ended voltage for the external voltage-controlled oscillator (VCO). The sigma-delta (Σ-Δ) based fractional interpolator, in conjunction with the N divider, enables programmable modulus, fractional-N division. Designers can implement a complete phase-locked loop (PLL) if the synthesizer is used with a VCO and an external loop filter.