6 GHz Fractional-N Frequency Synthesizer

ADF4156

Rev. 0

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FEATURES

RF bandwidth to 6 GHz

2.7 V to 3.3 V power supply

Programmable fractional modulus

Programmable charge pump currents

3-wire serial interface

Digital lock detect

Power-down mode

Pin compatible with

ADF4110/ADF4111/ADF4112/ADF4113/ADF4106/

ADF4153 and ADF4154 frequency synthesizers

Programmable RF output phase

Loop filter design possible with ADISimPLL

Cycle slip reduction for faster lock times

APPLICATIONS

CATV equipment

Base stations for mobile radio (WiMAX, GSM, PCS, DCS,

SuperCell 3G, CDMA, WCDMA)

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

Wireless LANs, PMR

Communications test equipment

GENERAL DESCRIPTION

The ADF4156 is a 6 GHz fractional-N frequency synthesizer

that implements local oscillators in the upconversion and

downconversion 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 sigma-delta (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))). The RF output phase is programmable for

applications that require a particular phase relationship between

the output and the reference. The ADF4156 also features cycle

slip reduction circuitry leading to faster lock times without the

need for modifications to the loop filter.

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.

FUNCTIONAL BLOCK DIAGRAM

LOCK

DETECT

N COUNTER

CP

RFCP3 RFCP2

RFCP4

RFCP1

REFERENCE

DATA

LE

32-BIT

DATA

REGISTER

CLOCK

AGND

DGND

DGND

CPGND

CE

OUTPUT

MUX

MUXOUT

–

+

HIGH Z

PHASE

FREQUENCY

DETECTOR

ADF4156

THIRD ORDER

FRACTIONAL

INTERPOLATOR

MODULUS

REG

FRACTION

REG

INTEGER

REG

CURRENT

SETTING

×2

DOUBLER

5-BIT

R COUNTER

CHARGE

PUMP

CSR

/2

DIVIDER

Figure 1.