ADRF6520 Dual Programmable Filters and VGAs for 2 GHz Channel Spacing for μW Radios

The ADRF6520 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 wanted 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 ADRF6520 ideal for quadrature-based (IQ) communication systems with dense constellations, multiple carriers, and nearby interferers. The filter corners, enable, and DC offset correction loop enable are all programmable via a serial port interfacter (SPI) port.

The first VGA that precedes the filters offers 27 dB of continous gain control with a maximum gain of 18 dB and sets a differential input impedance of 100 Ω. The filters provide a four-pole Butterworth response with 1.0 dB corner frequencies: 36, 72, 144, 288, 432, 576, and 720 MHz. For operation beyond 720 MHz, the filter can be disabled and completely bypassed, thereby extending the –1 dB BW up to 1.25 GHz. A wideband RMS detector is availalbe to monitor the signal at the filter inputs. A fixed gain amplifier of 6 dB immediately follows the filter. The post filter VGA provides 27 dB of continuous gain control with a maximum gain of 21 dB. The output buffers offer an additional 9 dB gain and provide a differential output impedance of 20 Ω. They are capable of driving 1.5 V p-p into 100 Ω loads at better than 55 dBc HD3. Independent, built-in dc off set correction loops for each channel can be disabled via the SPI if fully dc-coupled operation is desired. The high-pass corner frequency is determined by external capacitors on the CHP1 and CHP2 pins and the postfilter VGA gain.

The ADRF6520 operates from a 3.15 V to 3.45 V supply and consumes a maximum supply current of 410 mA. When fully disabled, it consumes <5 mA. The ADRF6520 is fabricated in an advanced silicon-germanium BiCMOS process and is available in a 32-lead, exposed pad LFCSP. Performance is specified over the –40°C to +85°C temperature range.

Applications

Features and Benefits

Matched VGAs and programmable filters

Continuous gain control range: 54 dB

Filter bypass mode I or Q badwidth (BW)

±1 dB gain flatness: >1250 Hz

4-pole Butterworth filter I or Q BW: 36 MHz to 720 MHz

RMS detector

IMD3: >55 dBc for 1.5 V p-p composite output

HD2, HD3: >55 dBc for 1.5 V p-p output

Noise Figure: 10.4 dB at max gain

NF < 11 dB over 12 dB of VGA2 gain back-off

100 Ω differential input, low impedance output

Optional dc output offiset correction

SPI programmable filter corners and gain steps

Single 3.3 V supply operation with power-down failure

RF & Microwave

All VGAs

Data Sheets

Document	note
ADRF6520: Dual Programmable Filters and VGAs for 2 GHz Channel Spacing for µW Radios Preliminary Data Sheet (Rev. PrB)	PDF 1.61 M

Order Information

Part Number	Package	Packing Qty	Temp Range	Price 100-499	Price 1000+	RoHS
ADRF6520ACPZ-R7 Pre-Release	LFCSP:LEADFRM CHIP SCALE	REEL 1500	-40 to 85C	0	0	Y

Evaluation Boards

Part Number	Description	Price	RoHS
ADRF6520-EVALZ	Evaluation Board	200	Y

ADRF6520: Dual Programmable Filters and VGAs for 2 GHz Channel Spacing for µW Radios Preliminary Data Sheet (Rev. PrB) adrf6520