950 MHz to 1575 MHz Quadrature Modulator

with Integrated Fractional-N PLL and VCO

ADRF6750

Rev. A

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FEATURES

I/Q modulator with integrated fractional-N PLL and VCO

Gain control span: 47 dB in 1 dB steps

Output frequency range: 950 MHz to 1575 MHz

Output 1 dB compression: 8.5 dBm

Output IP3: 23 dBm

Noise floor: −162 dBm/Hz

Baseband modulation bandwidth: 250 MHz (1 dB)

Output frequency resolution: 1 Hz

Functions with external VCO for extended frequency range

Power supply: 5 V/310 mA

GENERAL DESCRIPTION

The ADRF6750 is a highly integrated quadrature modulator,

frequency synthesizer, and programmable attenuator. The

device covers an operating frequency range from 950 MHz

to 1575 MHz for use in satellite, cellular and broadband

communications.

The ADRF6750 modulator includes a high modulus fractional-N

frequency synthesizer with integrated VCO, providing better

than 1 Hz frequency resolution, and a 47 dB digitally controlled

output attenuator with 1 dB steps.

Control of all the on-chip registers is through a user-selected

power supply ranging from 4.75 V to 5.25 V.

FUNCTIONAL BLOCK DIAGRAM

QBBP

QBBN

RSET

TESTLO

TESTLO

SDI/SDA

CLK/SCL

SDO

CS

TXDIS

AGND

DGND

×2

DOUBLER

5-BIT

DIVIDER

REFERENCE

CHARGE

PUMP

CURRENT SETTING

REFIN

REFIN

÷2

PHASE

FREQUENCY

DETECTOR

+

–

OUTPUT

STAGE

VCO

CORE

0°/90°

REGOUT

VCC1

VCC2

VCC3

VCC4

ADRF6750

VREG1

VREG2

VREG3

VREG4

VREG5

VREG6

LOMONP

LOMONN

RFOUT

47dB

GAIN CONTROL

RANGE

N-COUNTER

INTEGER

REGISTER

FRACTIONAL

REGISTER

MODULUS

THIRD-ORDER

FRACTIONAL

INTERPOLATOR

RFCP4 RFCP3 RFCP2 RFCP1

CP

LF3

LF2

LDET

IBBP

IBBN

CCOMP1

CCOMP2

CCOMP3

VTUNE

3.3V

REGULATOR

SPI/

INTERFACE

Figure 1.