Dual Fractional-N/Integer-N

Frequency Synthesizer

Data Sheet

ADF4252

Rev. E

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FEATURES

3.0 GHz fractional-N/1.2 GHz integer-N

2.7 V to 3.3 V power supply

Programmable dual modulus prescaler

RF: 4/5, 8/9

IF: 8/9, 16/17, 32/33, 64/65

Programmable charge pump currents

3-wire serial interface

Digital lock detect

Power-down mode

Programmable modulus on fractional-N synthesizer

Trade off noise vs. spurious performance

APPLICATIONS

Base stations for mobile radio (GSM, PCS, DCS, CDMA, WCDMA)

Wireless handsets (GSM, PCS, DCS, CDMA, WCDMA)

Wireless LANs

Communications test equipment

CATV equipment

GENERAL DESCRIPTION

The ADF4252 is a dual fractional-N/integer-N frequency

synthesizer that can be used to implement local oscillators (LO)

in the upconversion and downconversion sections of wireless

receivers and transmitters. Both the RF and IF synthesizers

consist of a low noise digital phase frequency detector (PFD), a

precision charge pump, and a programmable reference divider.

The RF synthesizer has a Σ-Δ-based fractional interpolator that

allows programmable fractional-N division. The IF synthesizer

has programmable integer-N counters. A complete phase-locked

loop (PLL) can be implemented if the synthesizer is used with

an external loop filter and voltage controlled oscillator (VCO).

Control of all the 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.

FUNCTIONAL BLOCK DIAGRAM

ADF4252

2

DOUBLER

OUTPUT

MUX

4-BIT

R COUNTER

PHASE

FREQUENCY

DETECTOR

LOCK

DETECT

CHARGE

PUMP

REFERENCE

24-BIT

DATA

REGISTER

CLK

DATA

LE

2

DOUBLER

CHARGE

PUMP

PHASE

FREQUENCY

DETECTOR

MUXOUT

FRACTIONAL-N

RF DIVIDER

INTEGER-N

IF DIVIDER

15-BIT

R COUNTER

Figure 1.