LT5568-2

1

55682f

GSM RF OUTPUT POWER (dBm)

–10

0

1

3

4

5

–6

–2

0

2

–106

–104

–100

–98

–96

–102

–8

–4

2

4

6

55682 TA02

EVM

NOISE

GSM/EDGE Optimized,

High Linearity Direct

Quadrature Modulator

performance wireless applications, including wireless

infrastructure. It allows direct modulation of an RF signal

using differential baseband I and Q signals. It supports

GSM, EDGE, CDMA, CDMA2000 and other systems that

operate in the 850MHz to 965MHz band. It may be config-

ured as an image reject upconverting mixer, by applying

90° phase-shifted signals to the I and Q inputs. The I/Q

baseband inputs consist of voltage-to-current converters

that in turn drive double-balanced mixers. The outputs of

these mixers are summed and applied to an on-chip RF

transformer, which converts the differential mixer signals

to a 50Ω single-ended output. The four balanced I and Q

baseband input ports are intended for DC coupling from a

source with a common mode voltage level of about 0.5V.

The LO path consists of an LO buffer with single-ended

input, and precision quadrature generators that produce

the LO drive for the mixers. The supply voltage range is

4.5V to 5.25V.

■

Infrastructure Tx for GSM/Cellular Bands

■

Image Reject Up-Converters for Cellular Bands

■

Low-Noise Variable Phase-Shifter for 700MHz to

1050MHz Local Oscillator Signals

■

RFID Reader

■

Optimized Image Rejection for 850MHz to 965MHz

■

High OIP3: +22.9dBm at 900MHz

■

Low Output Noise Floor at 5MHz Offset:

No RF: –159.4dBm/Hz

■

Integrated LO Buffer and LO Quadrature Phase

Generator

■

50Ω AC-Coupled Single-Ended LO and RF Ports

■

50Ω DC Interface to Baseband Inputs

■

Low Carrier Leakage: –43dBm at 900MHz

■

High Image Rejection: –52dBc at 900MHz

■

16-Lead 4mm × 4mm QFN Package

850MHz to 965MHz Direct Conversion Transmitter Application

APPLICATIO S

FEATURES

DESCRIPTIO

TYPICAL APPLICATIO

GSM EVM and Noise

vs RF Output Power at 900MHz

90

°

0

°

LT5568-2

BASEBAND

GENERATOR

PA

VCO/SYNTHESIZER

RF = 850MHz

TO 965MHz

100nF

x 2

EN

5V

V-I

V-I

I-CHANNEL

Q-CHANNEL

BALUN

55682 TA01

I-DAC

Q-DAC

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.