ADRF6518

The ADRF6518 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 ADRF6518 ideal for quadrature-based (IQ) communication systems with dense constellations, multiple carriers, and nearby interferers. The various amplifier gains, filter corners and other features are all programmable via a serial port interface (SPI) port.

The first VGA that precedes the filters offers 24 dB of continuous gain control with fixed gain options of 9 dB, 12 dB, and 15 dB, and sets a differential input impedance of 400 Ω. The filters provide a six-pole Butterworth response with 0.5 dB corner frequencies from 1 MHz to 63 MHz in 1 MHz steps. For operation beyond 63 MHz, the filter can be disabled and completely bypassed, thereby extending the −3 dB BW up to 1100 MHz. A wideband peak detector is available to monitor the peak signal at the filter inputs. The pair of VGAs that follow the filters each provides 24 dB of continuous gain control with fixed gain options of 12 dB, 15 dB, 18 dB, and 21 dB. The output buffers offer an additional option of 3 dB or 9 dB gain and provide a differential output impedance of less than 10 Ω. They are capable of driving 1.5 V p-p into 400 Ω loads at better than 65 dBc HD3. The output common-mode voltage defaults to VPS/2 and can be adjusted down to 900 mV via the VOCM pin. Independent, built-in dc offset 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 OFS1 and OFS2 pins and the postfilter VGA gain.

The ADRF6518 operates from a 3.15 V to 3.45 V supply and consumes a maximum supply current of 400 mA. When fully disabled, it consumes <1 mA. The ADRF6518 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