LT5546

1

5546f

s

17MHz I/Q Lowpass Output Noise Filters

s

Wide Range 1.8V to 5.25V Supply Voltage

s

Frequency Range: 40MHz to 500MHz

s

THD < 0.14% (–57dBc)

s

IF Overload Detector

s

Log Linear Gain Control Range: –7dB to 56dB

s

Baseband I/Q Amplitude Imbalance: 0.2dB

s

Baseband I/Q Phase Imbalance: 0.6

°

s

7.8dB Noise Figure at Max Gain

s

Input IP3 at Low Gain: – 1dBm

s

Low Supply Current: 24mA

s

Low Delay Shift Over Gain Control Range: 2ps/dB

s

Outputs Biased Up While in Standby

s

16-Lead QFN 4mm

× 4mm Package with Exposed Pad

40MHz to 500MHz VGA

and I/Q Demodulator with

17MHz Baseband Bandwidth

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

Total Harmonic Distortion vs

IF Input Level at 1.8V Supply

s

GPS IF Receivers

s

Satellite IF Receivers

s

VHF/UHF Receivers

s

Wireless Local Loop

EN

STBY

+

–

+

–

GND

1.8V

C2

1

µF

C1

1nF

C3

1.8pF

STANDBY

2xLO

560MHz

INPUT

280MHz

IF INPUT

C3

10pF

5546 TA01

÷2

LT5546

L1

15nH

L2

15nH

L3

39nH

C5

3.3pF

C4

3.3pF

GAIN CONTROL

ENABLE

IF DET

The LT

quadrature demodulator with variable gain amplifier (VGA)

and 17MHz I/Q baseband bandwidth designed for low volt-

age operation. It supports standards that use a linear modu-

lation format. The chip consists of a VGA, quadrature down-

converting mixers and 17MHz lowpass noise filters (LPF).

The LO port consists of a divide-by-two stage and LO

buffers. The IC provides all building blocks for IF down-

conversion to I and Q baseband signals with a single

supply voltage of 1.8V to 5.25V. The VGA gain has a linear-

in-dB relationship to the control input voltage. Hard-clip-

ping amplifiers at the mixer outputs reduce the recovery

time from a signal overload condition. The lowpass filters

reduce the out-of-band noise and spurious frequency

components. The –3dB corner frequency of the noise

filters is approximately 17MHz and has a first order roll-

off. The standby mode provides reduced supply current

and fast transient response into the normal operating mode

when the I/Q outputs are AC-coupled to a baseband chip.

IF INPUT POWER EACH TONE (dBm)

–60

–25

–30

–35

–40

–45

–50

–55

–60

–50

–40

–30

–20

5546 TA01b

–10

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO