Dual RF PLL Frequency Synthesizers

ADF4206/ADF4208

Rev. A

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FEATURES

ADF4206: 550 MHz/550 MHz

ADF4208: 2.0 GHz/1.1 GHz

2.7 V to 5.5 V power supply

Selectable charge pump supply (VP) allows extended

tuning voltage in 3 V systems

Selectable charge pump currents

On-chip oscillator circuit

Selectable dual modulus prescaler

RF2: 32/33 or 64/65

RF1: 32/33 or 64/65

3-wire serial interface

Power-down mode

APPLICATIONS

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

Base stations for wireless radio (GSM, PCS, DCS,

CDMA, WCDMA)

Wireless LANS

Communications test equipment

CATV equipment

GENERAL DESCRIPTION

The ADF420x family of dual frequency synthesizers are used

to implement local oscillators in the upconversion and down-

conversion sections of wireless receivers and transmitters. Each

synthesizer consists of a low noise, digital, phase frequency detector

(PFD); a precision charge pump; a programmable reference

divider; programmable A and B counters; and a dual modulus

prescaler (P/P + 1). The A (6-bit) and B (11-bit) counters, in

conjunction with the dual modulus prescaler (P/P + 1), implement

an N divider (N = BP + A). In addition, the 14-bit reference

counter (R counter) allows selectable REFIN frequencies at the

PFD input. The on-chip oscillator circuitry allows the reference

input to be derived from crystal oscillators.

A complete phase-locked loop (PLL) can be implemented if the

synthesizers are used with an external loop filter and voltage

controlled oscillators (VCOs).

Control of all the on-chip registers is via a simple 3-wire

interface. The devices operate with a power supply ranging

from 2.7 V to 5.5 V and can be powered down when not in use.

FUNCTIONAL BLOCK DIAGRAM

OSCILLATOR

CLK

DATA

LE

22-BIT

DATA

REGISTER

MUXOUT

ADF4206/ADF4208

CPRF1

CPRF2

PHASE

COMPARATOR

OUTPUT

MUX

14-BIT RF2

R-COUNTER

OSCIN

RF1INA

RF1INB

V

DD1

V

DD2

V

P1

V

P2

AGND

RF1

DGND

RF1

DGND

RF2

AGND

RF2

SDOUT

RF2

PRESCALER

RF2INA

11-BIT RF2

B-COUNTER

6-BIT RF2

A-COUNTER

RF2INB

OSCOUT

N= BP + A

CHARGE

PUMP

RF2

LOCK

DETECT

14-BIT RF1

R-COUNTER

RF1

PRESCALER

11-BIT RF1

B-COUNTER

6-BIT RF1

A-COUNTER

N=BP +A

RF1

LOCK

DETECT

PHASE

COMPARATOR

CHARGE

PUMP

Figure 1.