Fractional-N Frequency Synthesizer

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).

A key feature of the ADF4154 is the fast-lock mode with a builtin 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.

* RF bandwidth 500 MHz to 4 GHz

* 2.7 V to 3.3 V power supply

* Separate VP allows extended tuning voltage

* Programmable dual-modulus prescaler 4/5, 8/9

* Programmable charge pump currents

* 3-wire serial interface

* Analog and digital lock detect

* Power-down mode

* Pin compatible with the ADF4110/ADF4111/ADF4112/ADF4113/ADF4106 and ADF4153

* Programmable modulus on fractional-N synthesizer

* Trade-off noise versus spurious performance

* Fast-lock mode with built-in timer