The ADF4154 is a fractional-N frequency synthesizer that implements local oscillators in the up conversion and down conversion sections of wireless receivers and transmitters. It consists of a low noise digital phase frequency detector (PFD), a precision charge pump, and a programmable reference divider. There is a Σ-Δ based fractional interpolator to allow programmable fractional-N division. The INT, FRAC, and MOD registers define an overall N-divider (N = (INT + (FRAC/MOD))). In addition, the 4-bit reference counter (R-counter) allows selectable REFIN frequencies at the PFD input. A complete phase-locked loop (PLL) can be implemented if the synthesizer is used with an external loop filter and a voltage-controlled oscillator (VCO).