31 MHz, Dual Programmable Filters

and Variable Gain Amplifiers

Data Sheet

ADRF6516

Rev. C

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FEATURES

Matched pair of programmable filters and VGAs

Continuous gain control range: 50 dB

Digital gain control: 15 dB

6-pole Butterworth filter: 1 MHz to 31 MHz

in 1 MHz steps, 1 dB corner frequency

Preamplifier and postamplifier gain steps

IMD3: >65 dBc for 1.5 V p-p composite output

HD2, HD3: >65 dBc for 1.5 V p-p output

Differential input and output

Flexible output and input common-mode ranges

Optional dc offset compensation loop

SPI programmable filter corners and gain steps

Power-down feature

Single 3.3 V supply operation

APPLICATIONS

Baseband IQ receivers

Diversity receivers

ADC drivers

Point-to-point and point-to-multipoint radio

Instrumentation

Medical

FUNCTIONAL BLOCK DIAGRAM

ENBL

VPSD

COMD

LE

CLK

DATA

SDO

COM

VPS

OPP1

OPM1

COM

GAIN

VOCM

COM

OPM2

OPP2

INP1

INM1

VPS

ADRF6516

COM VICM OFS1

VPS

COM

INP2

INM2

VPS

COM OFDS OFS2

VPS

SPI

Figure 1.

GENERAL DESCRIPTION

The ADRF6516 is a matched pair of fully differential, low noise

and low distortion programmable filters and variable gain

amplifiers (VGAs). Each channel is capable of rejecting large

out-of-band interferers while reliably boosting the desired signal,

thus reducing the bandwidth and resolution requirements on the

analog-to-digital converters (ADCs). The excellent matching

between channels and their high spurious-free dynamic range

over all gain and bandwidth settings make the ADRF6516 ideal

for quadrature-based (IQ) communication systems with dense

constellations, multiple carriers, and nearby interferers.

The filters provide a six-pole Butterworth response with 1 dB

corner frequencies programmable through the SPI port from

1 MHz to 31 MHz in 1 MHz steps. The preamplifier that precedes

the filters offers a SPI-programmable option of either 3 dB or 6 dB

of gain. The preamplifier sets a differential input impedance of

1600 Ω and has a common-mode voltage that defaults to VPS/2

but can be driven from 1.1 V to 1.8 V.

The variable gain amplifiers that follow the filters provide 50 dB

of continuous gain control with a slope of 15.5 mV/dB. Their

maximum gains can be programmed to various values through

the SPI. The output buffers provide a differential output impedance

of 30 Ω and are capable of driving 2 V p-p into 1 kΩ loads. The

output common-mode voltage defaults to VPS/2, but it can be

adjusted down to 700 mV by driving the high impedance

VOCM pin. Independent, built-in dc offset compensation loops

can be disabled if fully dc-coupled operation is desired. The

high-pass corner frequency is defined by external capacitors on

the OFS1 and OFS2 pins and the VGA gain.

The ADRF6516 operates from a 3.15 V to 3.45 V supply

and consumes a maximum supply current of 360 mA when

programmed to the highest bandwidth setting. When disabled,

it consumes <9 mA. The ADRF6516 is fabricated in an advanced

silicon-germanium BiCMOS process and is available in a 32-lead,

exposed paddle LFCSP. Performance is specified over the −40°C

to +85°C temperature range.