lmh6514sqx National Semiconductor Corporation, lmh6514sqx Datasheet

lmh6514sqx

Manufacturer Part Number

lmh6514sqx

Description

Lmh6514 600 Mhz, Digital Controlled, Variable Gain Amplifier

Manufacturer

National Semiconductor Corporation

Datasheet

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LMH6514

600 MHz, Digital Controlled, Variable Gain Amplifier

General Description

The LMH6514 is a high performance, digitally controlled vari-

able gain amplifier (DVGA). It combines precision gain control

with a low noise, ultra-linear, differential amplifier. Typically,

the LMH6514 drives a high performance ADC in a broad

range of mixed signal and digital communication applications

such as mobile radio and cellular base stations where auto-

matic gain control (AGC) is required to increase system dy-

namic range. When used in conjunction with a high speed

ADC, system dynamic range can be extended by up to 42 dB.

The LMH6514 has a differential input and output allowing

large signal swings on a single 5V supply. It is designed to

accept signals from RF elements and maintain a terminated

impedance environment. The input impedance is 200Ω re-

sistive. The output impedance is either 200Ω or 400Ω and is

user selectable. A unique internal architecture allows use with

both single ended and differential input signals.

Input signals to the LMH6514 are scaled by a highly linear,

digitally controlled attenuator with seven accurate 6 dB steps.

The attenuator output provides the input signal for a high gain,

ultra linear differential transconductor. The transconductor

differential output current can be converted into a voltage by

using the on-chip 200Ω or 400Ω loads. The transconductance

gain is 0.1 Amp/Volt resulting in a maximum voltage gain of

+32 dB when driving a 200Ω load, or 38 dB when driving the

400Ω load. On chip digital latches are provided for local stor-

age of the gain setting. The gain step settling time is 5 ns and

care has been taken to reduce the sensitivity of bandwidth

and phase to gain setting.

The LMH6514 operates over the industrial temperature range

of −40°C to +85°C. The LMH6514 is available in a 16-Pin,

thermally enhanced, LLP package.

Typical Application

LMH™ is a trademark of National Semiconductor Corporation.

300429

Features

■

Key Specifications

■

Applications

■

Adjustable gain with a 42 dB range

Precise 6.02 dB gain steps

Parallel 3 bit gain control

On chip register gain setting

Fully differential signal path

Single ended to differential capable

200Ω input impedance

Small footprint (4 mm x 4 mm) LLP package

600 MHz bandwidth at 100Ω load

39 dBm OIP3 at 75 MHz, 200Ω load

26 dB to 38 dB maximum gain

Selectable output impedance of 200Ω or 400Ω.

8.3 dB noise figure

5 ns gain step switching time

100 mA supply current

Cellular base stations

IF sampling receivers

Instrumentation

Modems

Imaging

Differential line receiver

January 24, 2008

30042901

www.national.com

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