Abstract
It briefly introduced The Fractional-N Frequency Synthesizer ADF4154 microcontroller function, internal structure, pin array and typical apply circuit. 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 program-mable fractional-N division. The INT, FRAC, and MOD regis-ters 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).
A key feature of the ADF4154 is the fast-lock mode with a built-in timer. The user can program a predetermined count-down time value so that the PLL will remain in wide bandwidth mode, instead of having to control this time externally.
Control of all on-chip registers is via a simple 3-wire interface. The device operates with a power supply ranging from 2.7 V to 3.3 V, and can be powered down when not in use.
KEY WORD：
Separate VP dual-modulus prescaler charge pump 3-wire serial interface
Digital lock detect fractional-N synthesizer Fast-lock mode with built-in timer
