LTC6412

1

6412f

TYPICAL APPLICATION

DESCRIPTION

800MHz, 31dB Range

Analog-Controlled VGA

The LTC

with linear-in-dB analog gain control. It is designed for

AC-coupled operation in IF receiver chains from 1MHz

to 500MHz. The part has a constant OIP3 across a wide

output amplitude range and across the 31dB gain control

range. The output noise (NF + Gain) is also flat versus gain

to provide a uniform spurious-free dynamic range (SFDR)

>120dB over the full gain control range at 240MHz.

The LTC6412 is ideal for interfacing with the LT

LT5557 downconverting mixers, LTC6410-6 IF amplifier

and the LTC6400/LTC6401/LTC6416 ADC drivers for use

in 12-, 14-, and 16-bit ADC applications.

The LTC6412 recovers quickly from an overdrive condition,

and the EN pin allows for a fast output signal disable to

protect sensitive downstream components. Asserting the

SHDN pin reduces the current consumption below 1mA

for power-down or sleep modes.

3.3V Fully Differential 240MHz IF Receiver Chain with 31dB Gain Control

FEATURES

APPLICATIONS

n

800MHz –3dB Small-Signal Bandwidth

n

Continuously-Adjustable Gain Control

n

–14dB to +17dB Linear-in-dB Gain Range

n

35dBm OIP3 at 240MHz Across All Gain Settings

n

10dB Noise Figure at Maximum Gain

n

(IIP3 – NF) = +8dBm at 240MHz Across All Gains

n

2.7nV/√Hz Input Referred Noise

n

Differential Inputs and Outputs

n

50Ω Input Impedance Across all Gains

n

Single Supply Operation from 3V to 3.6V

n

110mA Supply Current

n

4mm

× 4mm × 0.75mm 24-Pin QFN Package

n

IF Signal Chain Automatic Gain Control (AGC)

n

2.5G and 3G Cellular Basestation Transceivers

n

WiMAX, WiBro, WLAN Receivers

n

Satellite and GPS Receiver IF

+IN

10nF

0.1μF

BPF

GND

6412 TA01

LTC2208

0.1μF

3.3V

1nF

0.1μF

180nH

180nH

3.3V

3.3V

3.3V

+OUT

–OUT

+

–

–OUT

+OUT

10nF

10nF

0.1μF

0.1μF

0.1μF

GAIN CONTROL

(+ SLOPE MODE)

IF INPUT

LTC6400-8

–IN

LTC6412

–IN

2.2μF

VGA Gain vs Frequency

Over Gain Control Range

FREQUENCY (MHz)

–20

–10

0

10

20

1

100

1000

10000

6412 G01

–30

10

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Technology Corporation. All other trademarks are the property of their respective owners.